Pseudotsuga Douglasii. 
175 
The Embryo. 
With the organization of the first segmentation spindle, the membrane 
of the fusion-nucleus becomes very indefinite, and gradually fades out com- 
pletely. As indicated in Figs. 34 and 35, the axis of the spindle comes to 
lie nearly at right angles to the long axis of the archegonium. During the 
period of the disorganization of the nuclear membrane an interesting 
observation was made in connexion with the numerous nucleoli-like bodies 
which are so abundant in the mature egg-nucleus, and from which the 
chromatin proper becomes segregated. As shown in Fig. 35, these 
granules, which stain like chromatin, collect at one side of the first spindle, 
and numerous kinoplasmic threads develop among them as if a second 
spindle were in process of formation. These threads show all the charac- 
teristics of regular spindle fibrils, especially those found in the early stages 
of spindle-formation. Whether this second pseudo-spindle ever develops 
farther I am unable to say, but it is certainly a point of cytological interest 
that these discarded chromatin-like granules should become associated with 
kinoplasmic threads as the chromosomes do in the regular spindle. The 
behaviour of these granules would suggest a close relationship with 
chromatin. 
The result of the division of the fusion-nucleus is indicated in Fig. 37. 
The daughter-nuclei remains in the upper part of the egg until the second 
mitosis takes place. The four free nuclei of the pro-embryo now pass 
to the base of the archegonium and are found in the positions represented 
in Figs. 38 and 39. These early stages in the development of the embryo, 
as well as the later ones, are essentially as in Pinns. The free nuclei 
enlarge considerably as they descend towards the base of the egg and 
become enveloped by dense granules of cytoplasm. The archegonium thus 
becomes differentiated into two regions — a basal nutritive region containing 
the pro-embryo, and an upper clearer region which is not so rich in food- 
granules. This differentiation is, however, not so clearly marked as in the 
Cupressineae or in Cephalotaxus (Lawson, ’ 07 ). The four free nuclei now 
at the base of the archegonium undergo further division. The latter, how- 
ever, result in the formation of walls between the nuclei as shown in Fig. 40. 
Eventually there are three tiers of cells and a tier of free nuclei. The 
uppermost of these tiers becomes the ‘ rosette ’, the middle tier becomes 
the suspensors, and the end tier the embryo proper. 
By the rapid elongation of the suspensor cells the embryo is carried 
deep into the tissue of the prothallium. This is shown in Fig. 41. Asso- 
ciated with the elongation of the suspensors a peculiar differentiation of the 
contents of the base of the archegonium was observed. The cytoplasm in 
this region becomes replaced by a homogeneous mucilaginous substance 
which apparently acts as a resisting plug to the growing suspensors. 
