[Vol. 6 

 304 ANNALS OF THE MISSOl'HI BOTANICAL GARDEN 



ally became less. In some cases this was due to the disap- 

 pearance of some of the algal forms but usually the amount of 

 an individual form also decreased. Protoderma was always 

 more abundant towards the surface than at the greater depths. 



The time in which the growth was first perceptible in the 

 cultures varied from about 3 weeks to 3 months. This was 

 dependent no doubt upon the amount of algae and also upon 

 the amount in a vegetative condition in the soil. Obviously, 

 vegetative cells would produce a growth in less time than spores. 



The resistance of these algae to desiccation was demonstrated 

 in series B-F inclusive, in which i;he cultures were allowed to 

 evaporate for a period of about 18 months, from March, 1917, 

 to November, 1918. The cultures became quite dry within 

 several months, so that the algae were exposed to desiccating 

 conditions for about 12 months. In the fall of 1918, the cultures 

 were reexamined and in most cases the algae seemed in a healthy 

 condition. After the cultures were moistened vigorous growth 

 occurred again. Especially noticeable was the fact that while 

 many of the vegetative cells of Ulothrix and Stick ococcus were 

 plasmolyzed, very few of the Protoderma cells showed any 

 injurious effects. 



The following is a list of the algae found in the cultures and 

 the greatest depth at which they occurred: 



Protoderma viride Kiitzing 100 cm. 



Hantzschia amphioxys (Ehr.) Grim 100 cm. 



Navicula aiemoides Grun 100 cm. 



Trochiscia ? 80 cm. 



Stichococcus bacillaris Nageli 70 cm. 



Oscillatoria amphibia Agardh 70 cm. 



Cladophora sp 60 cm. 



Ulothrix variabilis Kiitzing 60 cm. 



Anahaena sp 20 cm. 



Nitzschia Kiitzingiana Hilse 20 cm. 



Nostoc muscorum Agardh 20 cm. 



Oscillatoria chlorina Kiitzing 20 cm. 



Oscillatoria subtilissima Kiitzing 20 cm. 



Scytonema Hofmanni Agardh 20 cm. 



Oscillatoria anoerna (Kiitzing) Gomont Surface 



Oscillatoria formosa Bory Surface 



Oscillatoria splendid a Greville Surface 



