422 
STRUCTURE AND LIFE HISTORIES 
duced, consisting usually, in the white pine, of only four 
cells, all in the same plane; the number of these cells is 
somewhat variable. No neck-canal cells are formed ; only 
the egg, and the ventral canal-cell (the sister-cell of the 
egg) which disorganizes early (Fig. 312). 
FIG. 312. White pine (Pinus Strobus). Vertical section through the 
upper part of an ovule, shortly before fertilization, s.n, sperm-nuclei; 
st.c, stalk-cell; t.n, tube-nucleus; arch, archegonium; e.n, egg-nucleus. 
(After Margaret C. Ferguson.) 
374. Male Gametophyte. The germination of the 
microspore consists chiefly of a series of cell-divisions, all 
within the wall of the microspore. The first three 
divisions result in the formation of four cells, namely, two 
prothallial cells, one mother-cell of the antheridium, and a 
