Allen . — -The Spermatogenesis of Poly trichum juniperinum. 287 
until the moment of fertilization. Another conspicuous body, irregular in 
form, which appears in the cytoplasm of the mother-cell, passes into one of 
the two antherozoids and is described also as persisting to the time of 
fertilization. The latter is, perhaps, the only structure so far reported in 
plants which may be imagined to be in any way comparable with the sex 
chromosomes of animals — with the important difference that the resulting 
cytological differentiation between the male germ cells of Ginkgo is in no 
way connected with chomosome reduction. The case is of special interest 
because of the strict dioecism of Ginkgo. 
The van Leeuwen-Reijnvaans (1908) describe a small chromatic body 
in the androcyte of Polytrichum , distinct from the blepharoplast and the 
limosphere, which at one stage lies in contact with the nucleus and also, to 
judge from their figure, with the posterior end of the blepharoplast. It is 
likely that this body is the percnosome. The ‘accessory body’ described 
by Wilson ( 1911 ) in the androcytes of P oly trichum , A trichum , and Pellia 
is also probably in general to be identified with the percnosome. 
Walker ( 1913 ) shows in several of his figures a small but conspicuous 
cytoplasmic body (in his Fig. 34 there are two such bodies) in the androcyte 
of Polytrichum. This body, which is without much doubt also the 
percnosome, is shown in several cases, notably in his Fig. 3.6, as lying at the 
posterior end of the blepharoplast. Walker seems to consider the body so 
located to be the blepharoplast itself — the long cord which is really the 
elongated blepharoplast being taken by him for a distinct structure. 
Nothing shown in Woodburn’s ( 1915 ) figures of the spermatogenesis of 
Mnium is recognizable with any degree of certainty as the percnosome. In 
one case (his Fig. 15) he shows a small body lying in a vacuole ; in another 
(his Fig. 14) there is a similar appearance, but in this case he describes the 
body in question as probably lying upon the surface of the vacuole, and the 
‘vacuole’ itself, which is partly surrounded by a darkly stained layer, is 
evidently the limosphere. Lewis ( 1906 ) and Miss Black ( 1913 ) likewise find 
a single large vacuole, but nothing resembling the percnosome, at certain 
stages in the history of the androcytes of Riccia natans and R. Frostii. 
Apparently no previous writer has recognized the structure that I have 
called the apical body . However, Walker ( 1913 ) figures in certain cases 
what is probably this body ; especially in his Fig. 33, which shows two 
structures side by side that are quite certainly the limosphere and the newly 
formed apical body, the latter being in contact with the anterior end of the 
blepharoplast. 
