On the Retention of Vitality by Alga. 107 
during very long periods of rest, and that the length of time after 
which they can resume growth appears to be affected, in some 
cases at least, by the degree of dryness of the soil during the 
resting period. 
The greatest power of resistance against desiccation was shown 
by the two algae Nostoc museonan Kutz. and Nodularta Harveyana 
(Thvvaites) Thuret, which resumed growth after extreme desiccation 
for seventy years: Nostoc Passerinianum Bornet et Thuret, 
Anabcena oscillarioides Bory var .tevrestris n. var., Cylindrospennum 
lichenifonne (Bory) Kutz. and Chlorococcum humicola (Naeg.) Rabenh. 
resumed growth after fifty-nine years’ rest; Trocliiscia aspera 
(Reinsch) Hansg. Stichococcus bacillaris Naeg. and Nitzschia Palea 
(Kiitz.) W. Sm. after forty-eight years’ rest; Plectonema Battersii 
Gomont, Hapalosiphon flexuosus Borzi forma (?) and Phormidium 
teuue (Menegh.) Gomont after forty-seven years’ rest and Anabcena 
laxa A. Br. (?) after forty-six years’ rest. 
The algae described from these cultures differ in some respects 
from typical forms, but are probably only cultural forms of the 
given species. 
In conclusion 1 desire to express my thanks to Professor G. S. 
West, not only for suggesting that I should undertake this work, 
but also for his valuable help and advice throughout the course of 
the investigation. 
Botanical Laboratory, 
University of Birmingham. 
