Embryo of Cryptomeria Jctponica. 419 
In all the later stages the entire prothallium was removed. Nearly all of 
the dissections were made while the ovules were immersed in the killing 
fluid. 
After remaining in the fixing fluids from ten to twenty-four hours, the 
material was washed in running water from four to six hours. In 
transferring the material through the various grades of alcohol, Schleicher 
and Schull’s diffusion shells were used in the manner described in my work 
on Sequoia (’ 03 ). Bergamot oil preceded the infiltration of paraffin. 
Microtome sections from 2 /u to 8 ju, in thickness were made and the 
albumen fixative was used. For differentiating the various cell-structures, 
the triple stain, safranin gentian violet and orange G, gave the most 
satisfactory results. 
The Male Gametophyte. 
The staminate cones make their appearance as early as the first week 
in October, although pollination does not take place until March of the 
following spring. During the latter part of October and the early part of 
November, male cones in all stages of development may be found. From 
collections made during this period it was found that the reduction division 
of the microspore mother-cell, which leads to the formation of the tetrads, 
occurs about the first week of November. This, however, is not always the 
case, for we frequently find well-developed pollen-grains and very young 
sporangia not yet showing the mother-cells in the same cluster of cones. 
Generally the tetrads have separated and the pollen-grains are formed 
before the first of December. 
At first the microspores are more or less spherical in form, are 
surrounded by a thin membrane, and contain a deeply staining centrally 
situated nucleus (PL XXVII, Fig. 1). Very soon after they are formed 
they enlarge slightly and the thin membrane develops into a hard thick 
wall. During the thickening of the wall a small hook-like projection is 
developed from one side, as shown in Fig. 2. About four or five weeks 
before pollination, the nucleus of the pollen-grain enlarges and prepares for 
division. The spindle showing this division was not found, but material 
collected at this time showed two distinct nuclei in each pollen grain. One 
of these nuclei is much larger than the other. The larger one was 
generally found near the centre of the spore, while the smaller one was very 
frequently found lying against the spore-wall. The cytoplasm surrounding 
the smaller nucleus was much more dense than the rest of the cytoplasm 
in the spore. I am indebted to Professor Campbell 1 for calling my 
attention to the plasmic membrane which separates the two nuclei, and 
which I was at first unable to detect. Fig. 3 represents a section of the 
pollen-grain soon after it reaches the micropyle ; by this time the plasmic 
1 Campbell’s University Textbook of Botany, 1902, p. 324. 
Gg 
