216 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Methods. 
The most satisfactory fixing solution used in this work was Flem¬ 
ming’s stronger formula although Merkel’s and the chromacetic solu¬ 
tion of Stevens were also employed to some extent. Neither of the 
latter, however, gave such precise cytoplasmic details as did the 
former. The material was washed and run through the alcohols in 
the usual manner and gradually brought into 45 ^ paraffin through 
chloroform and finally sectioned in 52 of 0 paraffin. Practically all 
staining was done on the slide in Flemming’s triple stain, although 
iron alum was also employed to some extent. 
For some time the form of the plants and particularly the rela¬ 
tion of the several organs to each other and to the basal cell offered 
a mechanical difficulty. It will be recalled that the various fertile 
hyphae radiate from the top of a basal cell so as to give a more or 
less hemispherical form to the top of the plant. Since the anthe- 
ridia are invariably on the lower side of the oogonia, the side nearer 
the basal cell, it is evident that only by chance could one hope to 
get median sections of both oogonia and antheridia at the same time. 
To overcome this difficulty the plants were run back through the 
alcohols into water where they were spread out on the slide so that 
as many as possible of the pairs of oogonia and antheridia were in 
the plane of the slide. After they were thus arranged, a cover glass 
was carefully put on in order to keep the plants flat and preserve 
the position of the sexual organs, and the whole was then brought, 
without being moved, gradually, into absolute alcohol where it was 
hardened. In this form they were run through chloroform and par¬ 
affin, embedded either singly or in piles in this flattened condition 
and were sectioned 3 to 5 micra thick in the plane of the flat¬ 
tened surfaces; in this way the sections were cut so as to give a 
series of views of the plants as they were originally arranged on the 
slide. The material fixed in Flemming’s solution was darkened, par¬ 
ticularly the older oospores whose sections contained one or more 
large, black, oil-like bodies. By soaking these sections for twenty- 
four hours in a solution of hydrogen peroxide and 70°/ o alcohol and 
then for an equal period of time in turpentine at the temperature of 
the paraffin bath, tli'fe blackened bodies were left a light yellow and 
the cytoplasm was particularly clear and distinct. 
