Mar., 1923] 
SHOWALTER — RICCARDIA PINGUIS 
151 
great numbers and young sporophytes were fairly numerous. On this and 
the following day ten lots of material were fixed in the field, using Flemming’s 
fixing solutions: the medium unmodified, and the strong diluted with an 
equal volume of distilled water. These gave equally good results; there was 
a slight shrinkage of the cells of the surface layer of the thallus and of the 
Text Fig. i. Photomicrograph of a portion of a male thallus bearing two antheridial 
branches, unstained, mounted in toto in balsam. X I2|. 
cells of the archegonia, and in most cases considerable shrinkage of the cells 
of the young embryos. Thalli on which sporophytes were observed to be 
developing were generally left undisturbed in the hope that material might 
later be available for a study of the reduction divisions. After washing and 
dehydrating to eighty percent alcohol, the plants were picked over care¬ 
fully under the binocular microscope and the male and female plants were 
separated. 
The male plants in these collections averaged about one half to two 
thirds the size of the female plants (this is true also of a small collection 
of male and female plants, which had grown intermingled, collected one 
week earlier in the region of Lake Wingra). Two weeks later, when the 
Waubesa region was again visited, very few antheridia were to be seen, 
and the male plants were growing vigorously. Subsequent observations, 
when the male and female plants could be distinguished only by the vestiges 
of sexual branches or by the presence of sporophytes, have convinced me 
that there is no pronounced difference between male and female plants 
as to size or luxuriance of growth except during the period of gamete 
production, and I am not sure that the difference during this period is 
always so distinct as it appeared to be in the collections just described. 
Attempts to test this point by extended cultural experiments have thus far 
failed. 
