Wilson. — Spermatogenesis in the Bryophyta. 433 
in breadth. The limosphere and the body already referred to are still to 
be seen within the spermatid. The cytoplasm is scanty, and with the 
exception of a small mass at the posterior end of the developing spermatozoid 
stains feebly. The staining capacity of the mass in question increases 
as the spermatozoid approaches maturity. Guignard (26 A) in his investi- 
gation of Sphagnum fimbriatum states that an amylaceous mass is present 
in the vesicle of the mature spermatozoid, and it is probable that this mass 
corresponds to the deeply staining portion of the cytoplasm found in Mnium . 
When the spermatid of this latter plant is treated with iodine solution the 
mass referred to stains reddish brown, and does not give the blue-black 
coloration characteristic of true starch. The nucleus cannot be distin- 
guished, but the thread and limosphere stain deeply (Fig. 44). No cilia 
could be distinguished even at this late stage, but it may be presumed that 
they arise from the blepharoplast, and in this case would be found attached 
to the anterior end of the spermatozoid. 
The occurrence of ‘ double 5 spermatids has been described in Mar- 
chantia by Ikeno ( 32 ), and in Milium hornum similar structures have been 
discovered in this investigation (Fig. 43). These spermatids are approxi- 
mately double the normal size, and very probably contain two nuclei, 
although in consequence of the difficulties in staining the outlines of these 
bodies could not be clearly distinguished. Two limospheres, two blepharo- 
plasts, and two thread-like structures could, however, be seen in each 
(Fig. 43). These ‘ double ’ spermatids were discovered in an otherwise 
normal antheridium. In Marchantia each pair of normal spermatids pro- 
duced by the final division is surrounded by the mother-cell wall, and no 
wall is formed between the two individuals. Since each ‘ double ’ spermatid 
is surrounded by a wall it appears that this is produced by the failure of the 
mother-cell to complete its division. In Mnium hornum , however, each 
normal spermatid is surrounded by a wall. The ‘ double ’ spermatids in 
this plant may also be produced by the failure of the spermatogenic cells 
to complete the final division, but obviously, similar evidence to that used 
in the case of Marchantia cannot be advanced. 
Atrichum undulatum. 
The structure of the antheridium of Atrichum undulatum is very 
similar to that of Mnium hornum. Here again the spermatogenic cells 
are easily distinguished from those forming the wall on account of the 
numerous large chloroplasts found in the latter. The spermatogenic cells 
are rather irregular in shape, being four or five sided. Each contains 
a large nucleus in which a deeply staining nucleolus is found. In this plant 
Beer ( 5 ) has pointed out that the nucleoli ‘ consist of a lightly coloured 
matrix in which are embedded a number of grains of chromatin’. Although 
this appearance 1 has occasionally been seen, it is not of constant occurrence. 
