NATURAL AREAS AND REGIONS 



653 



The color of the river water is a pale 

 brown, mainly caused by the stains 

 derived from the leaves of the Wallaba 

 tree (Eperua falcata Aubl.). Lowering 

 a white disk into the water, the color 

 is quite yellowish at the surface, be- 

 coming browner farther down and 

 before it disappears it acquires a dis- 

 tinctly orange tone. From eighteen 

 inches downward the color becomes 

 darker and darker and at 25 in. the disk 

 disappears. 



Occasionally during heavy rains quan- 

 tities of brownish yellow mud is brought 

 down in suspension, making the river 

 waters quite opaque. 



The temperature of the river water 

 from one ft. below the surface to the 

 bottom averages from 79° to 80°F. 



Within the research area there are a 

 number of small streams, most of which 

 are drains for the swampy regions. 

 Practically all are densely shaded, 

 narrow in width, meandering at all times 

 through and around the bases of forest 

 trees. 



Vegetation 



The flora of Kartabo has been studied 

 by no competent general botanist, and 

 in this resume I have attempted nothing 

 but an indication of the more con- 

 spicuous and abundant growths, par- 

 ticularly those which possess an im- 

 portant relationship with members of 

 the vertebrate fauna, either in the way 

 of food, homes or media of support and 

 progress. 



Fluviatile. Blue-green, red and brown 

 algae and diatoms are abundant but 

 no collections have been made of 

 them. Very remarkable purple algae 

 have been found in the stomachs of 

 puffers (Colomesus psittacus) but not 

 observed elsewhere. 



Littoral. The littoral fauna is sharply 

 delimited to between tide marks. 

 Where the current is swift near shore, 

 these forms are almost hidden by over- 

 hanging vines and lianas, dependent 

 from the high jungle trees which crowd 

 down to the very water. Along sandy 

 and sloping muddy shores they are 



spread out, but even in such places do 

 not extend more than a few yards from 

 the high tide mark. Specific associa- 

 tions are well marked in the littoral 

 flora — solid cultures of mangroves, 

 sedge, mucka-mucka and others. 



Mangroves, RhizopJiora mangle, find 

 root-hold in certain definite areas of 

 the gently sloping mud-flats, while 

 back of them on firm mud and sand are 

 the graceful sedges. Two species of 

 sedges are dominant, Eleocharis geni- 

 culata R. Br. and Cyperus sp. In spots 

 where the current is not too swift or 

 waves too violent, appear rank upon 

 rank of the aroid lily with the incon- 

 gruous name of mucka-mucka, Montri- 

 chardia arborescens (Linn^) Schott. 

 Here and there are small patches of 

 Horse Tails, Equisetum, hinting of 

 epochs long since past. In the last two 

 years, however, these plants have dis- 

 appeared from the Kartabo shores. 



Clustering around the sedge clumps 

 is a low, white-flowered Diodia, creeping 

 along the sand and helping the coarse 

 grasses to cling to the shifting grains. 

 The most conspicuous flower stalks of 

 the fore-shore are the tall shore gentians, 

 Coutoubea spicata Aubl. which hold up 

 their racemes of pinkish-white flowers 

 well above high tide level. 



One of the most valuable shore binders 

 is the rush-like herb Xyris tenella 

 Kunth. Hundreds of these little, grassy- 

 leaved plants take root beneath the 

 mangroves and their roots mat together. 

 With them occur the straggly, jointed 

 stems with the inconspicuous pea-like 

 flowers of Vandellia difusa Linne. 



On beaches of pure sand, fronting 

 disintegrating, soil-covered banks, the 

 plant association is of another char- 

 acter, all uniting to hold fast as much 

 as possible of the granitic talus which 

 now and then slides down in sandy 

 avalanches. Such is the beach directly 

 in front of the laboratory. 



Every inch of the precipituous bank 

 which ofl'ers foothold is covered with 

 representatives of the clearing fauna — 

 the pink and white Mazaruni primroses, 

 Sipanea pratensis Aubl. being the only 



