167 
Pseudotsuga Donglasii. 
a network. Suspended in this network — especially at the angles where the 
threads crossed one another— numerous irregularly-shaped granules were 
observed. Although these granules were undoubtedly chromatin, and 
although they stained more deeply than the thinner portions of the threads 
which constitute the reticulum, it was quite impossible to determine how 
much of the thread consisted of chromatin, and how much of linin. Indeed, 
as far as one could judge from its affinity for stain, the entire reticulum 
seemed to be made up of chromatin threads — staining less deeply in the 
thinner places and more deeply at the points where the threads intersected 
one another. 
Accompanying the enlargement of the nucleus and the organization of 
the loose chromatic reticulum as shown in Fig. 7, the approach of nuclear 
division was also indicated by changes in the cytoplasm. Immediately 
surrounding the nucleus, the cytoplasm becomes densely granular until 
a more or less definite zone is differentiated — this being the first step 
towards the organization of the achromatic spindle. Fig. 8 shows a slightly 
older stage where the dense zone of cytoplasm becomes still further differ- 
entiated into definite but very fine spindle fibrils. It will be observed that 
these fibrils at first appear only on one side of the nucleus— the remaining 
surface being quite free of them. The details of this spindle in Pinus have 
been carefully worked out by Miss Ferguson (’04), and here this same 
peculiarity of the early stages of spindle- formation has been observed. 
From a study of Fig. 8 it will be seen that during the differentiation of 
the spindle fibrils the nucleus has lost its reticular structure. The chromatin 
threads no longer form a network, but become much thicker, more granular, 
and stain much more deeply than in the stage represented in Fig. 7. The 
reticulum has given rise to the spireme. 
While the mature spindle of the dividing body-cell was not found, 
sufficient observations on the early stages of spindle-formation were made 
to convince me that no structures which could be interpreted as blepharo- 
plasts were present during the organization of the sperm nuclei. This, how- 
ever, is what one would naturally expect, for in the Abietineae as well as in 
all other Coniferales the last vestige of the motility of the male gamete 
disappeared with the specialization of the pollen-tube as a means of convey- 
ing the sperm nuclei into the egg. The next stage observed in Psetidotsuga 
was that at the time of fertilization. The two sperm nuclei, accompanied 
by the tube- and stalk-nuclei, were found just inside the archegonium. As in 
Pinus (Ferguson, ’04, Blackman, ’98, Coulter and Chamberlain, ’01), Abies 
(Miyake, ’03), Tsuga (Murrill, ’00) and Picea (Miyake, ’03), these nuclei are of 
unequal size — the functional one being quite twice the size ofits neighbour. 
These are represented in Fig. 36. 1 
1 The meaning and causes of this inequality of the sperm nuclei have already been fully 
discussed in this journal (Lawson, Ann. Bot., vol. xxi, No. LXXXII, 1907, pp. 292-3). 
