172 Lawson . — The Gametophytes and Embryo of 
were frequently met with. While these changes in the form of the chromatin 
were in progress, it was observed that the cytoplasm immediately sur- 
rounding the nucleus was also undergoing a change of structure. From 
the series of stages found it was evident that on the anterior and posterior 
(in regard to the long axis of the archegonium) surfaces of the nucleus, the 
cytoplasm becomes differentiated into delicate kinoplasmic threads. These 
threads or fibrils are the first indications of the achromatic spindles. At the 
two places where they appear the nuclear wall breaks down and the fibrils 
extend into the nuclear cavity, and there come in contact with the chromo- 
somes. The details of the further organization of the ventral canal spindle 
have been so fully described for Pice a (Miyake, ’03) and Pinns (Ferguson, 
’05), and agree so closely with my own observations on Pseudotsuga , that 
a further description is unnecessary. 
In Pseudotsuga — as in all other Abietineae where the development of 
the egg has been observed — a definite membrane is formed which separates 
the ventral canal cell from the egg. The position of this membrane is shown 
in Figs. 23, 24, 25, and 26. It will also be observed from these figures that 
the nucleus of the ventral canal cell immediately shows signs of disintegra- 
tion, while the nucleus of the egg descends towards the centre of the arche- 
gonium and becomes enormously enlarged. From the drawn-out appearance 
of the cytoplasm between the egg-nucleus and the ventral canal cell it would 
appear that the descent of the enlarged nucleus is quite rapid. A very 
characteristic appearance of the archegonium and the condition of the cyto- 
plasm is shown in Fig. 2 6. The membrane of the ventral canal cell persists 
up to the time of fertilization. The phylogenetic importance of this mem- 
brane has already been discussed in a previous memoir (Lawson, ’07). Its 
presence in the Abietineae and its entire absence in the Cupressineae, Taxo~ 
dineae, and Taxineae is certainly significant. 
In Fig. 28 are represented two mature archegonia ready for fertilization. 
Fertilization. 
It will be remembered that the pollen-tubes have attained a great 
length before they reach the nucellus. In this regard Pseudotsuga is quite 
unlike any other of the Abietineae in which the stages of fertilization have 
been studied. It is the rule among the Abietineae that the pollen is 
deposited directly upon the apex of the nucellus and the tissue of the latter 
is penetrated immediately by the growing tubes. It is remarkable that there 
should be this difference in the behaviour of the pollen-tubes of forms that 
are so closely related. It nevertheless demonstrates how plastic a structure 
the pollen-tube really is, and how unreliable is the evidence it affords for 
phylogenetic purposes. It will be remembered how unusual are the growth 
and distribution of the pollen-tubes in Sequoia (Lawson, ’04). Here also 
there is a very early growth, and their distribution, although irregular, is 
