70 
whether they are chiefly the response to sharply varying condi- 
tions of moisture on the same or adjacent islands. In the case of 
Croton Scoulert, the leaf shape varies strikingly from the var. 
Macraet, found on the desert coast of Indefatigable Island, to var. 
grandifolius of the moist interior. Transections showing the 
altitudinal range of species of the moist windward slopes and dry 
leeward slopes of all the larger islands (similar to the altitudinal 
tables for plants of the Academy Bay Region) would show a con- 
formity from island to island, and would probably go a long way 
toward an understanding of their complex flora. Due to the 
rough nature of the ground and the difficulties in transporting food 
and water, such studies would undoubtedly require a long time. 
On the other hand, the vegetation of Cocos Island appears com- 
paratively simple. Like most oceanic islands which have a wet 
tropical climate, the vegetation consists for the most part of ferns 
(often tree-like), orchids, and Welastomaceae. The species, as a 
whole, appear to be closely tied up with those of the adjacent 
pn) 
Central American mainland. 
Studies of Bidens 
The problem of the species and varieties of Bidens centering on 
the Hudson River in New York has interested me for a number of 
years; I have made large collections of this genus on the tidal 
shores of both the Hudson and Hackensack rivers. Also I have 
continued the growing of unusual types in the greenhouse, which 
is not difficult, since the species are annuals and mature rapidly. 
B. hyperborea, a northern species extending from James Bay to the 
Merrimac River in eastern Massachusetts, was found last year in 
the Hudson River. 
I have continued work on a flora of the Windham Valley in the 
northern part of the Catskill Mountains, an area which has been 
comparatively neglected by local botanists, and have made sub- 
stantial progress in the collection of material. 
From time to time, progress has been made in the complex genus 
Eleocharis. The plates and much of the manuscript for the group 
Tenuissimae, principally of tropical America and_ tropical 
Africa, are now ready. During the past year the Hleocharis 
pauciflora group was revised. ££. pauciflora is represented from 
