150 BOTANICAL GAZETTE [FEBRUARY 
they lie one over the other, is easily overlooked. It is difficult, 
therefore, to determine the proportion of pollen grains in which 
there are more than two. In A. balsamea about 8 per cent show a 
division of one or both of the original prothallial cells; in A. 
Vettchit and A. brachyphylla the number is smaller. In some cases 
Fics. 4-7.—Figs. 4, 5, A. balsamea at time of shedding, showing divisions of 
prothallial cells and division of body nucleus int le nuclei (m); fig. 5 shows nuclear 
division in stalk cell; figs. 6, 7, A. Veitchii, showing two male nuclei, two derivatives 
of stalk cell, and prothallial cells much flattened; lettering as in the last; all X610. 
the separating wall, if formed, becomes obliterated and the appeat- 
ance is that of nuclear division only (fig. 2). 
In approximately 1o per cent of the gametophytes the nucleus 
of the body cell divides before pollination into male nuclei. These 
are large and well developed, and imbedded in a common mass of 
protoplasm which is inclosed by the wall of the former body cell. 
