156 ARCHEGONIATES. 
THE ARCHEGONIUM. . 
The development of the archegonium in the Cycadacee and in 
Ginkgo, which is similar to that of Pzzzs, is too well known to require 
a detailed description in this place. The manner, however, in which 
the large central cell is nourished during its growth by the immediately 
surrounding cells of the prothallium is, if Ikeno’s observations be cor- 
rect, a phenomenon of a rather rare occurrence in the Gymnosperms, 
and merits some special mention. These surrounding cells, which are 
separated from the central cell by thick cellulose walls, are of a uniform 
size, each possessing dense cytoplasm and a large nucleus. Before 
the archegonium is full grown the nuclei of these cells show a fine and 
distinct threadwork; but, as this organ approaches maturity, the 
nuclei, with the exception of the nucleoli, are transformed into homo- 
Fic, 64.—Three cells from layer of prothallial cells immediately surrounding upper part of central cell 
of archegonium of Cycas, showing protoplasmic connections between these cells ; in B the beak of 
nucleus extends into plasmic bridge.—(After Ikeno.) 
geneous and diffusely staining bodies. This phenomenon is not confined 
solely to the cells forming the wall of the archegonium, but it may 
extend to adjacent cells of the prothallium. This nuclear change takes 
place only in cells near the upper part of the central cell. 
Goroschankin has shown that in the Cycadacee@ fine cytoplasmic 
connections exist between the central cell of the archegonium and the 
surrounding cells. From Ikeno’s figures it seems that the cytoplasmic 
strands in Cycas are relatively large, and that large granular plasmic 
masses pass over bodily into the central cell (Fig. 64, A, B). Fre- 
quently the nucleus itself will send out a beak or protuberance toward 
the nearest plasmic connection. Arnoldi (1900) finds that in several 
species of Pzzuws and in Addes the nuclei from the surrounding cells 
pass into the egg-cell. The prevalence of condensed nuclei in cells 
surrounding the upper part of the central cell is explained by Ikeno as 
