Tue Fioripa Keys 7 
went, in 1910, to Sugarloaf Key for the purpose of trans- 
piianting plants of A. sisalina, introduced upon that 
island several other useful fiber plants, including Agave 
zapupe from eastern Mexico and Furcraea cabuya from 
Costa Rica. The bulbules of Agave decipiens, which 
resemble those of A. sisalina, have sometimes n sold 
to unsuspecting colonists for those of the true fiber- 
producing Sisal. 
€ mangroves are perhaps the most important agent 
in land formation on the Florida Keys. I have already 
referred to those of the Isthmus of Panama. The accom- 
panying figure of Rhizophora mangle, reproduced from a 
photograph by Mr. Guy N. Collins, shows the beginning 
of an islet near Sugarloaf Key and illustrates in a striking 
manner how the arched roots can collect floating debris - 
borne by the currents, like the teeth of a great comb. 
This material in time becomes black mud and offers an 
inviting foothold for the various plants mney found ce 
associated with the mangroves. 
In addition to Rhizophora mangle, several other ee 
grovelike plants occur on the keys, but none of them — 
have the peculiar arched roots which characterize this es 
species. Conocarpus erectus, the ‘‘button mangrove,’” 
can be recognized by its small alderlike cones. Laguncu- a 4 
_ laria racemosa has peduncled spikes of small tubular _ og 
flowers, leathery ribbed fruit, fleshy and veinless io ae 
3 : , eo 
_nitida, the black mangrove, which I saw growing near 
Aspi a _ The flowers oe ae black ipa itts "Ford ida 
