94 MIDLAND NATURALIST. 
growth, some cell or group of cells acquiring the power of multiply- 
ing in all directions and becoming ultimately new plants. Six to 
ten new plants are often produced from a large old one 
This power of multiplication in radial direction not infre- 
quently is acquired by cells five or six layers inward from the cir- 
cumference though usually the cells on the perimeter alone become 
centers for the formation of new plants. 
We have found that Coleochaete scutata, at least in the vege- 
tative stage is not at alla rare plant, for there is hardly a single 
month in the year that one or other of the jars does not contain 
this plant in one or the other stages of development. Dr. G. S. 
West of the University of Birmingham has written me that though 
in vegetative stage it is common in England he has never seen it in 
fruit growing in the laboratory. Plants with antheridia and anth- 
erozoids we have had frequently, and nearly every culture shows 
these when the plants are young. Plants with divided carpospores 
I have found in the laboratory several years ago two or three 
times, and fixed material is still on han 
Desmids in conjugation have never been obtained by us in labo- 
ratory cultures, but such cultures were reported to me from the 
University of California. Vegetative Closterium is easily transferred 
to the laboratory, and there kept for a long time, continually 
dividing. Conjugating forms of small Spirogyra will appear usually 
in spring, as also such stages of Zygnema leiosperma. Larger jars 
of ten or more gallons capacity seem favorable to their growth. One 
to two gallon jars will often produce zygosporic material in spring 
when wellexposed to sunshine. I have found that it is at times 
only necessary to transfer Draparnaldia in early spring from its 
native habitat in ditches to the laboratory in shallow vessels, in 
which some organic matter such as bits of meat or flies are put 
when an abundance of zoospores will be produced. Chaetophora too 
will produce zoospores in the laboratory. Early in summer is also the 
best time to obtain sexual stages of Achlya, or fly-mould. This 
thrown into stagnant water from ponds first produce oogonia and 
antheridia and later zoospores exclusively. 
Though the water in aquaria where algae grow should never 
be completely changed at any time it is necessary to replace the 
water that disappears by evaporation. The plants will of course 
after a certain time remove all the salts that are present and serve 
_ as plant food. These salts can be supplied in two ways. Water is 
