ON CERTAIN LEAF-HAIR STRUCTURES. 253 
G. tartarea, Desy. Inhabits Tropical America and bears 
a dense coating of pure white powder. 
G. calomelanus, Kaulf. A native of the West Indies but 
also occurring at Rio Janerio, Peru and the Islands off the 
Western Coast of Africa. Its indument is white. 
G. pulchella, Linden. A native of Venezuela. The in- 
dument is pure white. 
G. sulphurea, Desy. Found in the West Indies, and bear- 
ing a bright yellow powder. 
G. argentea, Nutt. Inhabits the Mascaran Isles and N atal. 
Its indument is white or tinged with red. 
Of these species the only one to which I have had access 
in the living state is G. triangularis, and having devoted 
considerable study to the chemical constitution of its indu- 
ment, I can give a better account of it than of any of the 
plants under discussion. The general appearance of the 
hairs found on this species may be gathered from the accom- 
panying sketch. They are two-celled capitate hairs, which 
in the drawing appear to be entirely bare, since the envelop- 
ing indument was necessarily dissolved off in the process of 
preparation for the microscope. As seen on the frond dur- 
ing the earlier stages of its growth, they present the appear- 
ance of spherical masses of fine acicular crystals. ater 
they produce such a mass of enveloping material as to form 
a complete crust or covering through which the growing 
sporangia force their way. In size they may be compared 
with the spores of the fern itself, though they are rather 
smaller than these. 
The indument itself varies in color from pure white to a 
deep rich yellow, and in this particular seems to be governed 
both by the age of the frond and by the locality in which it 
is produced. It appears to consist of two distinct chemical 
compounds. The first, to which I have ventured to give the 
name ceroptene, is a light yellow crystalline body having the 
formula ©; Hig O, and melting at 135° OC. It forms beauti- 
ful triclinic crystals that have a decidedly resinous lustre 
