Cae ae SOM Tee a OAS on ree Fae See ee OA eee Oe ee ee Se Pen a eg ee ey 
1910] | CHAMBERLAIN—DIOON EDULE 427 
that point, but remain in the seed, sometimes until the seedling 
is three or four years old. 
e embryo may develop continuously, germinating without any 
resting period, or may germinate after a resting period. Seeds 
which had been in the laboratory for two years germinated readily, 
but how long they might retain their power of germination is 
uncertain. 
While the general course of development in the later stages of 
the embryo is the same in all of my material (Dioon, Ceratozamia, 
Zamia, Microcycas, and Encephalartos), there are considerable 
differences in details which may prove suggestive, and conse- 
quently no more detailed description will be given until a compara- 
tive study has been made. 
The development of the vascular system of the embryo and 
seedling of Dioon edule has been investigated in this er 
by TuressEn (7). 
Summary 
1. The liquid from the pollen tube causes a decrease in the 
turgidity of the neck cells, and this allows a portion of the upper 
part of the egg to escape, thus forming a vacuole at the top of the 
egg. The entire sperm is thus drawn into the egg 
2. There are sometimes nine, but oftener ten simultaneous free 
nuclear divisions, resulting in the formation of 512 or 1024 free 
nuclei. 
3- There is a complete but evanescent segmentation of the 
entire proembryo, the walls then disappearing except at the base 
of the proembryo, where they become permanent. 
4. The coleorhiza and root cap, although differing in appearance, 
cell structure, and in function, are formed from the same meristem, 
and both are morphologically root cap. 
5. Plerome, periblem, and dermatogen are differentiated quite 
late in the development of the embryo. 
6. The seed germinates without any resting period, but also has 
been germinated after a rest of two years. 
Tue University oF CHICAGO 
