1906] CHAMBERLAIN—OVULE OF DIOON 349 
Typical views are shown in figs. 33, 3 3a, and 34. Occasionally there 
is considerable enlargement (fig. 35), as is often the case in Pinus. I 
have a preparation of Encephalartos which not only shows a reorgani- 
zation and enlargement of the ventral canal nucleus, but the nucleus 
has moyed down from the papillate projection toward the egg, sug- 
gesting the possibility of fertilization of the egg by the ventral canal 
nucleus. In StRASBURGER’s account (33) of fertilization in Picea 
vulgaris and in CouLrer’s account (3) in Pinus Laricio, describing 
fusing nuclei of equal size, a large ventral canal nucleus was doubtless 
mistaken for a male nucleus, but that these were actual cases of 
fertilization of the egg by its own ventral canal nucleus there can 
be but little doubt. 
The egg and archegonial jacket—The egg of Dioon is the largest 
yet known in plants. It is seldom less than 4™™ in length and often 
Teaches a length of 5™™; the largest egg measured was 6™™ in length. 
The actual size, just after the formation of the ventral canal nucleus, 
is shown in fig. r7a. The egg at the right in this figure is shown again 
in fig. 17, which is magnified six diameters so as to show the com- 
parative size of the papilla, ventral canal nucleus, and egg nucleus. 
Before fertilization the egg nucleus becomes much larger and more 
deeply placed than is represented in this figure. In fig. 15, which 
shows the actual size of the central cell before the beginning of the 
archegonial chamber, and in fig. 16, showing the beginning of the 
archegonial chamber, the nucleus of the central cell is too small to 
be represented even by a single dot. 
The nutrition of the egg is practically the nutrition of the central 
cell, for it reaches its mature character before the mitosis which 
separates the ventral canal nucleus from that of the egg. Goro- 
SCHANKIN (8) in 1883 described a continuity of protoplasm between 
the jacket cells and egg of Ceratozamia. He believed that strands 
Piet protoplasm pass through sieve plates in the pits of the jacket. 
TKENo (10) in 1898 made a more detailed study of the growth of the 
€8g in Cycas. He also described protoplasmic continuity between 
the jacket cells and the egg, and a passage of proteid materials from 
the jacket into the egg. Miss Isapet SmirH (14), who studied the 
hutrition of the egg in Zamia floridana, found no connecting strands 
of protoplasm, but found projections, which she called haustoria, 
