No. 460.] STUDIES ON PLANT CELL.—V. 233 
about equal size whose chromatin contents unite in a fusion 
nucleus to form a common network in which male and female 
elements cannot be distinguished. A similar condition obtains 
in Cryptomeria, according to Lawson (:04b), where a fusion 
nucleus is described in which paternal and maternal chromatin 
are mingled together in a nucleus that passes through a short 
period of rest before the development of the first cleavage 
spindle. In view of the work on Pinus I think it may safely be 
questioned whether in Sequoia and Cryptomeria the maternal 
and paternal chromatin really does form a common network in 
the resting fusion nucleus. The subject is one very difficult of 
study and demands more stages than Lawson seems to have 
followed. 
Fertilization in the cycads is not as completely known as for 
the conifers. Webber (:01) figures the sperm nucleus of 
Zamia imbedded in the egg nucleus but quite distinct from it as 
in the pine but the further history leading to the development 
of the first segmentation spindle was not followed. On the 
other hand Ikeno ('98b) described in Cycas the formation of a 
cup-ike depression in the egg nucleus to receive the sperm 
nucleus which was said to enter and fuse completely with the 
female and the same author (Ikeno, : or) reports a complete 
fusion of the gamete nuclei in Ginkgo and did not distinguish 
the paternal and maternal chromosomes during the formation of 
the first segmentation spindle. However it is probable that 
more detailed. studies among the cycads and in Ginkgo will 
show a behavior of the sperm nucleus together with the pater- 
nal and maternal chromatin essentially similar to that of the 
conifers. All investigations among the cycads and in Ginkgo 
agree that cytoplasmic structures of the sperm (blepharoplasts, 
cilia, etc.) are left behind in the cytoplasm of the egg before the 
mete nuclei unite. ` 
© Our knowledge of the details of fertilization in the angio- 
sperms is surprisingly meager. The only account of the chro- 
matin is that of Mottier ('98 ; :04b, p. 176) for Lilium. He 
describes and figures the two gamete nuclei as uniting with 
their chromatin in the resting condition. The nuclear mem- 
branes disappear at the surface of contact and the two nuclei 
