Description: Up till now the lower deposits of peat (in Dutch: veen-op-groterediepte = peat at greater depth) have been investigated in the Netherlands mainly in the Western part of the country, viz. in the provinces of Noord-Holland, Zuid-Holland and Zeeland. The analyses have shown that the development of this, now comparatively well known peat layer must have begun either in the second half of the boreal period or else in the beginning of the atlantic one, and that it must have come to an end in the first half of the latter. Among the earlier investigators the botanist Mrs VERNEER-LOUMAN and some geologists had arrived at the conclusion that the sudden transgression of the North sea which made an end to the formation of peat, took place in the boreal period, and hat the whole lower deposit of peat, therefore, was of boreal age (lit. 7). This opinion, however, was sufficiently disproved by FLORSCH\xc3\x9cTZ, and all subsequent analyses have confirmed the view that the peat formation must have stopped early in the atlantic period (lit. 2, 3, 4). The same conclusion was arrived at by GODWIN as a result of his investigations of the lower peat found in SE England (lit. 5, 6) and by several German investigators as a result of their analyses of the lower peat, found in NW Germany.\nOnly one analyses of the lower peat in the province of Friesland, in the Northern part of the Netherlands, has sofar been published. The geologist VAN ANDEL found near Kiesterzijl, at a depth of only 3.50 m a thin layer of peat. He identified it with the lower peat from the W part of the Netherlands which occurs several meters deeper. His two diagrams show a boreal age for the basal layers and an atlantic age for the top ones and they confirm therefore the conclusions,obtained in the W part of the country (lit. 1).

Description: This study deals with the vegetation of about 125 former beds of the larger rivers in the Netherlands. It includes all communities of higher plants except the carrs, which are dealt with in a separate paper by Kop (1961). The investigation of the communities aimed at a knowledge of their floristic composition as well as at a definition of their habitat. The description and the classification of the units was carried out according to the concepts and methods of the Braun-Blanquet school (Braun-Blanquet, 1932, 1951; Becking, 1957). Moreover, among the former river beds types were recognized, characterized by a special set of communities and by correlated abiotical properties. A number of vegetation-units are described here for the first time, viz. The Polygoneto-Nymphoidetum (alliance Potamion) with the subass. typicum and the subass. potametosum pectinati. According to descriptions of vegetations found in the literature the subass. typicum is also present in former river beds of the Rhine in Germany about up to Bingen (LAUTERBRON, 1917); more to the south it is replaced by the Trapo-Nymphoidetum (OBERDORFER, 1957). The Sparganieto-Glycerietum fluitantis polygonetosum (alliance Glycerieto-Sparganion). The main difference with the habitat of the other subassociations (see MAAS, 1959), where the water is moving either permanently (brooks) or at least now and then (ditches), is that the vegetation is influenced by the current only during the shortlasting annual floods. The Cicuteto-Caricetum pseudocyperus (alliance Phragmition) is to be divided into two subassociations, viz. the subass. typicum and the subass. comaretosum. The main difference between the habitats of the two subassociations appears to be that the first is eutrophic and the second more mesotrophic. The Scirpetum triquetri et maritimi typhetosum (alliance Phragmition). In contrast with the other subassociations (see ZONNEVELD, 1960), this one occurs only in oligoto mesohalinic, stagnant water. The Caricetum elatae (alliance Magnocaricion) is revised. Carex hudsonii is the only characteristic species found throughout the area in which the association occurs. The community everywhere participates in the hydrosere on sand or peat. The following subdivision was made: Subass. typicum; the community is eutraphentous; according to the literature it is found in Switzerland (KOCH, 1926), S. Germany (OBERDORFER, 1957) and Belgium (LEBRUN c.s., 1949; VANDEN BERGHEN, 1952 a). Subass. comaretosum: more mesotraphentous than the subass. typicum; found in N. Germany (T\xc3\x9cXEN, 1937; PASSARGE, 1955 b) and the Netherlands. Of the Valerianeto-Filipenduletum (alliance Filipendulo-Petasition) two new subassocaitions are established, viz.: Subass. juncetosum; it is the replacing-community of a mesotraphentous variant of the Alnetum glutinosae. Subass. senecietosum; represented in the river forelands outside the tidal area; it replaces there an eutraphentous Salicion-community, and may be natural if the development of trees is prevented by ice-drift. Eight types of former river beds were distinguished. Two of these could be subdivided into some subtypes. Their classification according to their communities and their abiotical properties is summarized in table 26. Descriptions of habitats which more or less resemble one of these types of former river beds, are known from other parts of the Netherlands and from the adjoining parts of Germany and Belgium. However, as far as we know, of the types described by us, viz. those represented in the river forelands along the upper courses of the rivers, seem to differ from all habitats that have been described so far.

Description: The Brokopondo Lake in the interior of Surinam began to form when on 1 February 1964 the dam in the Surinam River near Afobaka was closed. The lake was intended to cover an area of about 150.000 ha and to have a maximal depth of about 47 m.\nThe basin, largely occupied by forest, was not cleared beforehand. During the initial stage the water in the flooded forest was characterised by a very high content of organic matter and the absence of oxygen. As the water level rose, differentiation between a hypolimnion and an epilimnion developed. The oxygen content of the epilimnion was high.\nDuring the first three years of its existence the lake attained an area of about 84.000 ha and a maximal depth of 38 m.\nWithin this period eight aquatic plant species became numerous in the lake. Special attention was paid to Eichhornia crassipes and Ceratopteris pteridoides. In April 1966, when the lake covered about 78.000 ha, the former had colonized 53%, the latter 21 % of this area. Since September 1966 both diminished greatly, Eichhornia as a result of artificial control, Ceratopteris for unknown reasons.\nFloating pieces of decaying wood became overgrown by a variety of plant species, 27 of which were recorded.\nMixed vegetations of water and marsh plants developed, free-floating mats ( Eichhornia being the matrix), patches attached to partly submerged tree tops, and belts along the shore. Twentytwo species were observed as constituents of these floating vegetations.

Description: Une \xc3\xa9valuation des plantes d\xe2\x80\x99apr\xc3\xa8s leur pouvoir \xc3\xa9dificateur de dunes doit \xc3\xaatre pr\xc3\xa9c\xc3\xa9d\xc3\xa9e d\xe2\x80\x99une description de leur structure a c\xc3\xb4t\xc3\xa9 de l\xe2\x80\x99\xc3\xa9tendue et de la densit\xc3\xa9 des organes a\xc3\xa9riens il faut consid\xc3\xa9rer d\xe2\x80\x99importance capitale et d\xc3\xa9cisive la structure des organes souterrains, tel que K\xc3\x9cHNHOLTZLORDAT (1923) et VAN DIEREN (1934) l\xe2\x80\x99ont sugger\xc3\xa9.\nLes organes souterrains peuvent \xc3\xaatre: des rhizomes, des racines, ou des tiges ensevelies par le sable meuble. Une comparaison des diff\xc3\xa9rentes qualit\xc3\xa9s m\xc3\xa8ne \xc3\xa0 la distinction de groupements et \xc3\xa0 la cr\xc3\xa9ation d\xe2\x80\x99un syst\xc3\xa8me.

Description: In this article, the second of a series of four, a number of swamp communities occurring along former river beds in the forelands of the great rivers in the Netherlands are dealt with according to the new classification of reed swamp and marsh communities (order Phragmitetalia, class Phragmitetea) in WESTHOFF & DEN HELD (1969). For more background information the reader is referred to VAN DONSELAAR (1961, 1971).\nThe association Typhetum angustifoliae (alliance Phragmition) can be recognized in the river forelands. There its composition is identical with that in stagnant fresh waters. However, a comparison with the communities of the backswamps in the fresh water tidal area (ZONNEVELD, 1960) makes it questionable whether the new classification can be applied there. The same question arises with regard to the Typhetum latifoliae (alliance Phragmition), an association of which our material is too scanty to permit extensive comparisons.\nTwo associations of the alliance Oenanthion are treated. The Rorippo-Oenanthetum is a characteristic community of former beds which are relatively strongly influenced by the current during the annual high water, so that formation of a peaty or even humic soil is prevented. It appears that there are no descriptions from other habitats in the Netherlands. A form of the Sparganio-Sagittarietum (without Sparganium emersum), present in a few former beds, is only briefly mentioned.

Description: Lianes, defined as woody climbers and (facultatively) straggling shrubs, were collected in an area of about 1900 square kilometres of the Brokopondo District, in the interior of Surinam. Ten different habitats were distinguished only one of which was intensively sampled, viz. the so-called \xe2\x80\x9chigh forest\xe2\x80\x9d, the most luxuriant climax vegetation type in the area.\nA total of 132 species were distinguished, 80 of which could be determined with certainty and 15 nearly so. Among the identified species one was new (described since as Dicranostyles guianensis A. Mennega, Conv.), and 5 were new records for Surinam, viz. Sparattanthelium aruakorum Tutin (Hern.), Abuta obovata Diels, Abula splendida Kruk. et Mold., and Sciadotenia sagotiana (Eichl.) Diels (all Menisp.), and Mimosa micracantha Benth. (Mim.).\nThe distribution of the species over the 10 habitat types is shown, and the ecology of some of them is discussed more in detail.

Description: Dans la v\xc3\xa9g\xc3\xa9tation des dunes du Languedoc J. BRAUN-BLANQUET (1952) distingue trois associations, \xc3\xa0 savoir; 1) l\xe2\x80\x99Agropyretum mediterraneum parmi et sur les premi\xc3\xa8res dunes basses; 2) l\xe2\x80\x99Ammophiletum arundinaceae sur les dunes plus hautes; et 3) le Crucianelletum maritimae dans les d\xc3\xa9pressions et en arri\xc3\xa8re des dunes. Or, il est \xc3\xa9tabli que le d\xc3\xa9veloppement de la premi\xc3\xa8re association et le passage de celle-ci \xc3\xa0 la deuxi\xc3\xa8me sont accompagn\xc3\xa9s d\xe2\x80\x99une \xc3\xa9dification de dunes, et que la troisi\xc3\xa8me provient de la d\xc3\xa9g\xc3\xa9n\xc3\xa9rescence de la deuxi\xc3\xa8me.\nK\xc3\x9cHNHOLTZ-LORDAT (1923) a le premier attir\xc3\xa9 l\xe2\x80\x99attention sur le r\xc3\xb4le essentiel jou\xc3\xa9 par la v\xc3\xa9g\xc3\xa9tation dans l\xe2\x80\x99\xc3\xa9dification des dunes du Languedoc. Les r\xc3\xa9sultats de ses recherches ont \xc3\xa9t\xc3\xa9 confirm\xc3\xa9s par VAN DIEREN (1934) aux Pays-Bas. Les deux auteurs ont \xc3\xa9tudi\xc3\xa9 le pouvoir accumulateur du sable par les parties a\xc3\xa9riennes des plantes; mais le premier seul donne aussi quelques indications sur le r\xc3\xb4le \xc3\xa9dificateur des parties souterraines.

Description: Humiria balsamifera (Aublet) St. Hil. var. balsamifera KH 3294, var. guianensis (Benth.) Cuatrecasas KH 2954, 3288, 3313. K: Widespread, but not common, in thickets. S: Northern and southern savannas, savanna scrub and savanna woods. R: Kaieteur savanna (var. guianensis).

Description: In February and early March, 1961, the senior author spent three weeks on a small savanna in the approximate centre of Suriname, South of Tafelberg, (map 1). He was accompanied by Mr. W. H. A. Hekking. The time was spent in exploring the flora of the savanna and the adjacent forest. As a detailed study of the vegetation of the savannas of northern Suriname was then in progress, several extensive papers being in preparation (Heyligers, 1963; Van Donselaar, 1965; Van Donselaar-Ten Bokkel Huinink, 1966), it was felt that a more thorough inventory of the vegetation and the flora of the savanna might be rewarding. When a general impression of the plant-cover of the area had been obtained, eight representative sample-plots were selected, their vegetation was analyzed and described after the method of the French-Swiss school of phytosociology, and pits were dug in the soil down to bedrock, samples being taken in every distinctive-looking layer. This work was carried out jointly by the senior author and W. H. A. Hekking; part of the floristic exploration was also done by or with Dr. R. M. Tryon, Harvard Herbarium, Cambridge, Mass. The results are here presented. It was felt that in order to integrate them with those obtained elsewhere in Suriname, the collaboration of a specialist familiar with the Suriname savannas in general was required. This was the junior author\xe2\x80\x99s task, who, after his prolonged work on the savannas of northern Suriname, later expanded his work to those of the southern part of the country. The preliminary results of the last-named study are in the press; more detailed field work is in progress as this paper goes to the press.

Description: At present 38 species of Rhynchospora, now including also Dichromena, are known from Suriname, two of which with two varieties. Two new species are described here: Rh. guianensis and Rh. sublanata. A key to the Suriname species is presented.\nFor every taxon the distribution and, where known, a brief characteristic of its ecology in Suriname are given.