5 
Embryo of Seqttoia sempervirens. 
It was found very desirable to use albumen instead of alcohol as a 
fixative. When the staining was not satisfactory, the sections fixed on 
the slide with albumen were bleached and restained without trouble. 
With the alcohol method, however, restaining was impossible, as the 
sections were invariably washed off the slide. By restaining, many 
valuable demonstrations were restored. 
The triple stain safranin, gentian, and orange G., was found to be 
the most satisfactory in differentiating the various cell-structures. 
The Male Gametophyte. 
The reduction-division of the microspore mother-cell leading to the 
formation of the tetrads takes place during the first week in December. 
The first division is rapidly followed by the second, and within a week 
or ten days after the first division the tetrads have separated and the 
pollen-grains formed. 
The microspores remain within the sporangium at least three weeks 
before pollination takes place. During this period they become larger, 
spherical in form, and surround themselves with a hard thick wall. The 
cytoplasm is very granular and contains a small amount of starch. The 
nucleus is comparatively small and is always centrally situated (PL I, Fig. i). 
While yet in the sporangium and about a week before pollination the 
nucleus of the microspore enlarges and divides ; so that at the time the 
pollen is shed there are two nuclei in each grain. Sections made before 
and after pollination showed a considerable difference in the size of the 
nuclei, the one being about twice the size of the other. The larger one 
was centrally situated, while the smaller one was invariably found near the 
spore wall. The smaller nucleus was surrounded by a sharply differen- 
tiated zone of very granular cytoplasm, which suggested the presence of 
a membrane between the two nuclei as shown in Fig. 2. The chromatin 
of the smaller nucleus was in the form of small granules closely packed 
together ; it consequently stained more deeply than the larger nucleus, 
where the meshes of the chromatin network appeared to be much more 
loosely arranged. A study of the further history of these nuclei has 
convinced me that the larger nucleus is the so-called tube-nucleus and 
the smaller one represents the generative cell. 
A very careful search was made with the hope of finding a vestige 
of the vegetative tissue of the gametophyte. One or more vegetative 
cells have been reported for the Cycads Ginkgo and Pinus> but a most 
searching examination failed to reveal even a vestige of such a cell or 
nucleus in Sequoia. I am strongly inclined to believe that the develop- 
ment of these evanescent structures has been entirely suppressed. 
Observations of two years indicated that pollination takes place 
during the first week in January, just about the time the female flowers 
