42 
to Ahorca Lagarto, a distance of 12.7 miles, taking photographs 
of trees, plant associations, etc., which will be of service in the 
lecture courses given in the Garden. On such trips I was able 
to secure, also, specimens of mosses, Hepaticae, fungi, fresh-water 
algae, etc. One plant that was found growing in abundance in 
the marshes between Mt. Hope and Mindi may prove of some 
sanitary interest and importance to the inhabitants of the Canal 
Zone. This was an Asol/a,a closely related species of which 
Fic. 14. 4:0¢/a on surface of water in a swamp between Mt. Hope and Mindi, 
Canal Zone. 
has been successfully used by European sanitary officials in the 
warfare against mosquitos and malaria. It is a small plant of 
moss-like habit, though allied to the ferns rather than to the 
ses. Certain species of this genus, when growing under 
favorable conditions, as was evidently the case in these Pana- 
manian marshes (Fic. 14) form floating masses so dense, that, it 
is said, they prevent mosquito-larvae, developing in the water 
below, from obtaining sufficient air, thus asphyxiating them or 
