436 Wilson. — Spermatogenesis in the Bryophyta . 
the nucleus becomes homogeneous. Elongation proceeds until the ends 
approach one another closely (Pl. XXXVIII, Fig. 59), but actual contact 
does not take place, the anterior usually passing to the outside of the 
posterior end (Fig. 60). 
The limosphere and the accessory body are still distinguishable in the 
cytoplasmic mass enclosed by the elongated nucleus (Fig. 60), and appa- 
rently are finally found in the vesicle. Although the remaining cytoplasm 
is scanty in amount, the portion towards the posterior end of the spermato- 
zoid stains strongly, and together with the limosphere and body, probably 
gives rise to a deeply-staining mass similar to that described by Guignard 
(26 a) in the vesicle of the spermatozoid of Sphagnum fimbriatum . At this 
stage the spermatozoid consists of about one and a half turns of a spiral, 
and although almost mature no cilia have been distinguished with certainty 
in the preparations. Presumably these are produced from the blepharo- 
plast, and are therefore attached to the anterior end of the spermatozoid. 
Pellia epiphylla. 
The antheridia of Pellia epiphylla usually appear at about the begin- 
ning of April, and development proceeds until the latter part of June. 
Towards the end of the period plants which have already borne antheridia 
frequently develop archegonia. Plants were preserved at intervals during 
the whole of this period in order to obtain all the stages of development. 
Several fixing fluids were employed, and satisfactory results were obtained 
with both of Flemming’s mixtures, Merkel’s fluid, and acetic alcohol. This 
last medium gave much better results with Pellia than with Mnium or 
A trichum. 
Material was obtained in the field and from Chelsea Physic Garden. 
After collection in the field, clumps of the undisturbed plants were brought 
into the laboratory and preserved at various times in the next few days. 
In some cases the plants were kept at a temperature of 28° C. for twelve hours 
preceding fixation. At the Physic Garden material was fixed either in the 
cool greenhouse where the plants were grown or after they had been placed 
for several hours in a greenhouse kept at a higher temperature. In all cases 
the air was removed from the tissues by means of an air-pump. Sections 
varying from 3 /x-7 ju, in thickness were cut, some being parallel to the longi- 
tudinal axis of the plant, some at right angles to this axis, and some 
parallel to the surface. The following stains were used : Flemming’s triple, 
Heidenhain’s haematoxylin, Breinl’s triple stain, and a mixture of acid 
fuchsin and iodine green. 
The spermatogenic cells in the young antheridia of Pellia generally 
appear four-sided in section, but their form is not nearly so regular as that of 
the corresponding cells in Marchantia and Fegatella (PI. XXXVIII, Fig. 61). 
The large nucleus is bounded by a definite membrane and contains a large 
