302 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1919. 
Nazia aliena, Anthephora hermaphrodita, V alota insularis, Paspalum 
paniculatum, Panicum fasciculatum, Cenchrus viridis, Manisuris 
granularis, All these species are common weeds in the West Indies. 
The mangrove formation is conspicuous along nearly the whole 
of the coast of British Guiana and extends along the banks of the 
rivers as far as the influence of salt water reaches. The tide is felt 
many miles inland, usually as far as the first rapids, that is, from 
30 to 60 miles, though the salt water may not reach this far. Salt- 
water plants are found in places where the surface water is fresh. 
It is probable that in such places the lower layers of salt or brackish 
water are overlain with fresh water. The chief species of trees 
making up the mangrove formation are black mangrove (/hizo- 
phora mangle), white mangrove (Laguncularia racemosa), courida 
(Avicennia nitida), and bindoree (Drepanocarpus lunatus). The 
black mangrove has glossy thick dark green leaves. The seeds 
germinate while still attached to the branches and the root extends 
down as a cylindrical brown object several inches long, looking like 
long pods. These finally fall off and the young plant falls into the 
mud or is carried by currents till it is stranded and then continues 
growth. The roots of the tree are arched and stilt-like, forming a 
tangled mass through which the tide rises and falls. The black 
mangrove appears to be more common along river banks than along 
the sea coast. 
The white mangrove has smooth leaves and white pubescent 
spikes of flowers, the hard nutlike fruits obovate and two-ridged. 
The courida has the leaves whitened beneath and produces large 
numbers of vertical air roots that come up through the soil in the 
vicinity of the plants. The binderee or bindoree pimpler is a vicious 
plant because of the numerous short firm recurved stipular prickles. 
This species belongs to the legume family and has racemes of rather 
small blue papilionaceous flowers and flat curved or lunate pods. 
On a sand flat near Kitty Village, a suburb of Georgetown, may 
be seen several characteristic shore plants. A creeping morning 
glory (Ipomoea pes-caprae) with upright flowering stems a foot 
or two tall is abundant. Other common species are a kind of salt 
grass (Sporobolus virginicus), seashore heliotrope (Heliotropium 
curassavicum) , with one-sided curved racemes of small white flowers, 
sea purslane (Seswvium portulacastrum), with spreading or creep- 
ing fleshy stems and pink star-shaped flowers in the axils of the 
leaves, salt-wort (Batis maritima), a semishrub a foot or two high 
growing in the mud around the mangroves, and love vine or dodder 
(Cuscuta sp.), a yellow leafless vine parasitic on the sea purslane. 
The coastal region, the alluvial plain extending several miles back 
from the coast, is to a considerable degree occupied by marshes. On 
