[Vor. 1 
26 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
the region of the upper column. Тһе lower portion was dis- 
carded, and the upper one was sealed, subsequently transferred 
to а sterile medium, and broken to permit the organisms, free 
from contaminations, to enter the medium and begin their 
development. 
By the gelatin plate method, Krüger (13) prepared pure 
cultures of two new organisms—Chlorella protothecoides and 
Chlorothecium | saccharophilum—obtained from the exudation 
of Populus alba. Tischutkin (23) lists representatives from 
about eighteen genera of algee—including diatoms, green, and 
blue-green forms—as having been obtained in pure culture 
by the agar plate method. After three or four successive dilu- 
tions in liquid one per cent agar, the organisms were plated in 
Petri dishes. The filamentous forms he washed in sterile water, 
cut into short segments, and transferred to the liquid medium. 
The methods given by Ward (24) include plating in agar and 
silicic acid jelly, though as a whole the methods are applicable for 
the separation of algal species rather than for their isolation in 
pure culture. This is especially true of the plaster of Paris, and 
precipitated calcium carbonate methods. Gonidia from Xan- 
thoria parietina, and Gasparinia murorum (Hoffm.) Tornab., to- 
gether with Pleurococcus vulgaris and Scenedesmus caudatus were 
obtained in pure culture by Artari (1). Chodat and Goldflus (8), 
by the use of pieces of sterilized unglazed porcelain in contact 
with a mineral nutrient solution, claim to have isolated a species 
of Nostoc in pure culture. Тһе procedure was a simple one, 
consisting in repeated transfers to fresh sterile plates until a 
pure culture was at length obtained. 
Several years later Chodat and Grintzesco (9) reported that 
by essentially the same method, Oocystis elliptica, Dictyo- 
spherium pulchellum, Kirchneriella lunaris, Rhaphidium poly- 
morphum, Pediastrum tetras, Scenedesmus acutus, Pleurococcus 
vulgaris, Hematococcus lacustris, and Chlorella vulgaris had 
been obtained in pure culture. In cases where the number of 
algal individuals is small, but the bacteria and fungi relatively 
abundant, the authors point out the desirability of first increas- 
ing the number of the former by introducing the mixture 
into a mineral nutrient solution favorable for the growth of 
the alge but not so for the fungi. Where filamentous forms are 
