PTERIDOPHYTA. 141 



the oval surface of the receptive spot, but had not penetrated the 

 plasma membrane. It had apparently untwisted and had begun to 

 reticulate, as its structure was somewhat granular or lumpy in appear- 

 ance. In still another instance the spermatozoid had just passed 

 through the plasma membrane at the receptive spot. The egg was 

 not collapsed, but quite turgid. The receptive spot was distinguished 

 from the rest of the cytoplasm only by the presence of fewer granules 

 and, perhaps, a little looser reticulum. Other eggs were observed in 

 a turgid condition (the archegonium being open) , into which no sper- 

 matozoid had penetrated, but the nucleus was concave on the upper 

 side. It may be mentioned that the nucleus is not always concave, 

 but may be rounded or globular. Apart from these instances the 

 observations of the author agree with those of Shaw. 



In about one-half hour, or less, after the entrance of the spermato- 

 zoid into the archegonium, the canal is closed by the expansion of the 

 four proximal neck-cells and the four just beyond them. The egg 

 recovers its turgidity and forces the free spermatozoids against the 

 outer wall of the venter (Fig. 56, D). A cellulose membrane does not 

 seem to be formed about the egg immediately, although, as stated by 

 Shaw, a very delicate cellulose wall may have been dissolved by the 

 chromic acid used in fixing. Soon after penetrating the egg the nucleus 

 of the spermatozoid enters the egg-nucleus before undergoing any 

 change in form or visible structure (Fig. 55, B). The fate of the 

 cytoplasmic part was not very satisfactorily followed, but all the facts 

 observed indicate that the cytoplasmic band and blepharoplast are left 

 in the cytoplasm of the egg, where, as in Cycas and Zamia of the 

 Gymnosperms, they are absorbed. In Fig. 56, D, a body lying near 

 the concave side of the nucleus bears some resemblance to the cyto- 

 plasmic part of the spermatozoid. The author has also observed in 

 several instances undoubted traces of the blepharoplast near the upper 

 surface of the nucleus, and there is no question but that the fate of 

 the blepharoplast and cytoplasm is as just stated. 



The egg-nucleus during the entire process of fecundation is in the 

 resting condition. Several conspicuous nucleoli are usually present. 

 They vary in size and have a vacuolate structure. In the delicate linin 

 network are distributed the small chromatin granules. 



In a short time the sperm-nucleus within the egg-nucleus begins to 

 reticulate, becoming visibly granular and of a looser structure. This 

 is apparent three hours after the entrance of the spermatozoid into the 

 archegonium (Fig. 56, D), but it may sometimes be seen earlier, after 

 thirty minutes or one hour. The time after which a change is notice- 



