FERTILISATION 29 
(Fig. 12, a). If prothalli be grown in moist air, and only watered by 
absorption from below, the archegonia will have no access to fluid water, 
Fic. 13. 
Fertilisation in Ouoclea sensibilis : the arrows indicate direction of the growing point of 
the prothallium. A. vertical section through an open archegonium probably within ten 
minutes after the entrance of the first spermatozoid. Xs500. A. vertical section of the 
venter of an archegonium containing spermatozoids, and the collapsed egg with a sperma- 
tozoid within the nucleus. Thirty minutes. X1200. (After Shaw.) 
and they will then remain closed, and fertilisation will be impossible; but 
if watered from above, as they would be in the ordinary course of Nature, 
the external fluid water will bathe them, 
and rupture will result. This may be 
observed in living archegonia which 
have been kept relatively dry, and then 
mounted in water under the micro- 
scope: the neck dehisces at the distal 
end owing to internal mucilaginous 
swelling, and its cells diverge widely: 
the canal-cell and ventral-canal-cell are 
extruded, and the ovum remains as a 
deeply seated, spherical protoplast, while. 
access to it is gained through the open 
channel of the neck (Fig. 12, B). Thus 
the same conditions lead to the rupture 
both of the male and female organs: 
in Nature a shower of rain would supply 
the necessary external fluid water, and 
would at the same time supply the 
Fic. 13 dzs. 
Horizontal section of an egg, showing coiled 
spiral male nucleus within the female. Twelve 
hours. Xz200. (After Shaw.) 
