180 MISS B. MURIEL BRISTOL ON A 
VIIT. SUMMARY. 
The material described has been obtained from cultures of a sample of 
dried soil, which was sent from the Malay States about two years before the 
cultures were set up. 
The vegetative cells are spherical or subspherical, solitary or collected 
together into mucilaginous strata, very variable in size, being from 20-80 u 
in diameter, each with a thin cellulose cell-wall and a single parietal 
ehloroplast containing from one to several pyrenoids and numerous starch 
granules. In adult cells a quantity of yellow oil is stored, in which a bright 
red pigment is often dissolved. 
The cytoplasm is reticulate. The young cells contain a single minute 
nucleus and one pyrenoid, both of which multiply by repeated division so 
that the adult cells are coonocytie with many pyrenoids, 
Propagation takes place, by successive bipartition of the contents of the 
mother-cell, into 8-16 or numerous biciliate zoogonidia which may develop 
asexually or may act as facultative gametes. In both cases direct develop- 
ment into vegetative cells takes place. 
Aplanospore-formation may also take place, preceded by the multipli- 
cation by constriction of the nuclei of the mother-cell. The aplanospores 
remain imbedded in a mucous stratum, and enter into a palmelloid state 
in which further bipartitions may take place. Eventually, the palmelloid 
cells either acquire cilia and behave as normal zoogonidia or they develop 
direetly into vegetative cells. 
True vegetative division does not take place, but the cell-contents may 
divide into two daughter-cells which immediately acquire new cell- 
walls and are set free as vegetative cells by the dissolution of the mother- 
cell-wall. 
Chlorococeum. humicola, differing in no essential partieulars from that in 
the Malay soil, has been found to occur almost universally in English soils. 
The limit of its resistance against desiccation and of its retention of vitality 
has been shown, by investigations on long-dried English soils, to lie some- 
where between seventy and eighty years, 
In conclusion, I wish to express my thanks to Professor G. S. West for his 
valuable help throughout this work. 
Dotanical Laboratory, 
University of Birmingham. 
