52 
Bristol.— On the Alga- Flora of some Desiccated 
observed to open as a lid. Within the mucilaginous investment a few 
divisions were observed to take place, resulting in the formation of a short 
irregular filament usually terminated at each end by a heterocyst. Hetero- 
cysts arranged in short series of two or three were often observed at 
a slightly later stage of development. It is probable that the cells of the 
Text-fig. 4. Nostoc commune , Vaucher, from arable soil, Tisbury, Wilts, h ., heterocyst; 
s.h., seriate heterocysts ; S A , spores of form A ; S B , spores of form B ; g.s ., germinating spore of form 
b ; f f young filament from germinated spore ; v. } vegetative cells of form a. All figs, x 825. 
young filaments divide irregularly after a time, since numbers of small 
colonies were observed in the cultures comparable to the juvenile forms 
described below. 
In other species of Nostoc direct germination into a short filament, as 
observed in N . commune , did not usually take place, and juvenile forms were 
