Cell Structure, Growth and Division in the Antheridia of Polytrichum etc. 127 
two membranes. His Statements were substantially confirmed by Bischoff 
(1834); they were contradicted, but later confirmed, by Valentine 
(1837, 1839); and were substantiated also by the extended studies of 
Lantzius-Beninga (1844, 1847) upon various Bryales and Sphagnum. 
Meyen (1839) contradicts von Mohl’s Statement that the spores are 
formed within a “mother cell”; he describes the division of a cell, by an 
ingrowth of its membrane, to form four spores. 
According to Schemper (1848), the division of the mother cell begins 
with the Separation of its granulär contents into four groups, each of 
which surrounds itself with a membrane; the mother cell membrane is 
partly or entirely dissolved, and the spores become free. 
Further descriptions of spore formation are given by Hofmeister 
(1851, 1867), Schimper (1858), Vaillant (1863), Sachs (1868), Kühn 
(1870), and Strasburger (1875), none of whom, however, supplies new 
cytological details. 
Overton (1893 a — b) finds that the details of karyokinesis in the 
spore mother cells of mosses correspond exactly with those observed in 
the pollen mother cells of seed plants and concludes that reduction occurs 
at this point, although the smallness of the nuclei makes an exact count 
of the chromosomes impossible. 
Beer (1903) reports f inding four chromosomes in dividing spore mother 
cells of Funaria hygrometrica; the chromosomes divide, forming eight, 
four of which pass to each daughter nucleus. Later (1906 a ), he announces 
that his count was incorrect, and that the chromosome number (in Funaria 
hygrometrica, Atrichum undulatum, Mnium hornum and Polytrichum juni- 
perinum) is far higher than he formerly supposed. 
According to Wilson (1908, 1909), each resting archesporial nucleus 
of Mnium hornum has a large nucleole, containing most of the chromatin, 
and a fine, homogeneous reticulum. In the prophases of mitosis, broad, 
band-like chromatin masses appear, which, becoming longer and narrower, 
form a spirem. The nucleole stains less deeply, loses its sharp outline, 
and finally breaks up and disappears. The spirem Segments into twelve 
chromosomes, which in the equatorial plate are slender and hook-sliaped. 
They split; the V-shaped halves pass to the poles and tliere fuse into 
an irregulär mass ; this mass loses its staining capacity and several nucleoles 
appear, which usually fuse into one. The spore mother nucleus contains 
a coarser reticulum than its ancestors, and a nucleole from which in most 
cases a small, rounded body is budded off; this body does not pass into 
the cytoplasm. The transformation of the reticulum into a spirem is 
followed by synapsis, after which the spirem becomes looser and thicker; 
