446 BOTANICAL GAZETTE [MAY 
disappears. During prophase of the ultimate division of the spermatogenous 
cells, the nucleolus divides into two separate masses by constriction, and before 
separation is complete, a third small body buds off from one of the nucleolar 
ies. These three bodies become free, but do not pass beyond the nuclear 
membrane, and the smallest one is considerably larger than is usually associated 
with centrosomes. These bodies were lost during later prophase, and their fate 
could not be determined. Chromosomes are constantly 6 in number and no 
difference in size could be observed. 
he daughter nuclei at first contain several deeply staining granules, which 
later are replaced by a single centrally placed nucleolus. This nucleolus 
divides by constriction into two bodies, one of which again divides. The 
nuclear membrane then becomes indistinct, and two of the nucleolar bodies 
pass out into the cytoplasm, and probably increase by division, as more than 
two can often be found. Later they become rodlike and are usually grouped 
near a vacuole. At this stage the nucleus is barely distinguishable as a mass 
somewhat denser than the surrounding cytoplasm. The nucleolus may again 
cut off one or two bodies, which probably pass out into the cytoplasm and 
become associated with the rodlike bodies. These rods now increase in length, 
become irregularly curved, and look very much like chromosomes. Their 
number is usually three or four. This situation would seemingly explain the 
double reduction of J. and W. Docters vAN LEEUWEN-REIJNVAAN. The 
nucleolus now enters upon a third period of division, giving rise to two bodies 
which pass out into the cytoplasm, one being most likely the blepharoplast , 
the other WILson thinks is perhaps the same as the “‘ Nebenkérper”’ described 
in Marchantia by IkENo. All but one or two of the rodlike bodies now coalesce 
and form a spherical mfass, which the author names the “‘limosphere.’’ Later, 
when the limosphere is seen in optical section, it appears as a ring. In the last 
stages studied (the nearly mature sperms) the limosphere still persisted. | 
In Atrichum undulatum the sequence is much the same as in Mnium. No 
centrosomes could be found, and the chromosome number is 17. In Pellia 
epiphylla, centrospheres and perhaps centrosomes are present in later divisions 
in the antheridium. The author thinks the blepharoplast may be derived from 
the centrosome. A limosphere and accessory body are present in the sperm, 
but their origin was not determine 
ILsoN’s work gives evidence er extremely careful study, and seems to 
furnish a satisfactory explanation for the fantastic performances which have 
been reported as taking place during spermatogenesis in Musci.—W. J. G 
LAND. 
of the mitotic figure—Lawson’s? study of the microspore 
mother cells of Disporum, Gladiolus, Yucca, Hedera, and the vegetative cells 
in the root tip of Allium has revealed a series of stages in the development of 
; ¢ Lawson, A. ANSTRUTHER, Nuclear osmosis as a factor in mitosis. Trans. Roy. 
Soc. Edinburgh 48:137-161. pls. 1-4. 1911 
