296 BOTANICAL GAZETTE [APRIL 
2. *‘Prothallial cells’’ 
Several species have been described in which the “prothallial”’ 
cell has the power of division. Among the number are Ginkgo 
biloba, by STRASBURGER (1); Picea excelsa, by MIYAKE (2) and 
Pottock (3); Abies balsamea (9); Agathis, by JEFFREY and 
CHRYSLER (14); Podocarpus, by CoKER (13a); and Dacrydium 
by Miss Youne (16). The similarity of the generative cell and 
the prothallial cells is pointed out by Miss Younc: “In Dacrydium, 
as in Podocarpus and Abietineae, a third cell is cut off from the 
main body of the spore. It overlies the others and is so similar 
to them that, but for its subsequent behavior, one might think it a 
prothallial cell. It is the generative cell, generative in the sense 
that it is the ancestor of the spermatogenous cell. This and the 
second prothallial cell now divide.” The first prothallial cell may 
also divide. Again: “at shedding the pollen grain contains the 
body cell and five free nuclei. The nucleus of the body cell is in- 
distinguishable from those of the prothallial cells and the tube 
nucleus.” Poxtock (3) states that in a large proportion of the 
gametophytes of Picea excelsa there is only one prothallial cell. 
BURLINGAME (20) says: “in Podocarpus one primary prothallial 
cell may be cut off, after which the free nucleus divides to form the 
free spermatogenous cell and the tube nucleus; or two primary 
cells may be cut off before the tube nucleus is separated from the 
primary spermatogenous cell.’”’ In these two species, as well as in 
Picea canadensis, the antheridial function is not limited to a defi- 
nite primary derivative. It has been established that “prothallial 
cells” and generative cells may be similar in appearance; that 
frequently they are similar in their power of division; the simi- 
larity is further emphasized by the presence of “prothallial cells” 
in the pollen tube. The present account has emphasized the 
similarity in the origin, and has shown that potentially there is 
a similarity in function; that any one or sometimes two of the 
primary derivatives may be antheridial. To what extent we 
are justified in suggesting that these phenomena are indicative 
of a multi-antheridial ancestral form only further research can 
determine. 
