1909] SAXTON—WIDDRINGTONIA CUPRESSOIDES 167 
in the sporophyte, collections at 9 A. M., 12 noon, and 6 or 7 P.M. 
show an approximately similar number of nuclear figures. 
It is noticeable in fig. 8 that the nuclei project slightly into the 
vacuole. Later on the layer of cytoplasm thickens considerably 
and the nuclei are then completely sunk in it. Figs. 9 and ro 
indicate the principal changes met with after the last stage figured. 
Fig. 9 shows clearly the process of wall formation in the prothallus, 
Fic. 2.—Widdringtonia cupressoides (see text). Xt. 
alveoli being organized as described by SoKOLOWA (35) and other 
Writers for various gymnosperms. The cells at first formed are 
Invariably uninucleate, and the original cell walls persist. The 
binucleate and multinucleate condition met with later (see below) 
does not arise, therefore, in the same way as the binucleate prothallus 
cells of Cryptomeria described by Lawson (21). The pollen tube 
has meanwhile reached the tip of the prothallus, and even before 
wall formation begins, it penetrates the megaspore membrane and 
8tows down just inside of it, on or near the surface of the prothallus, 
to about one-third or one-half way down. 
ig. 10 is drawn from the same series of sections as fig. 9 and 
represents the tip of the pollen tube which has in this way pene 
