382 Harper.—Sexual Reproduction in Pyronema 
the nuclei in multinucleated gametes is not to be regarded as 
conclusive evidence on this point, even if it bears at all upon 
it. It is merely a proof that the nuclei are the structures 
especially entrusted with the function of sexual reproduction, 
and certainly is not good ground for deciding that multi¬ 
nucleated protoplasmic masses are to be considered as tissues 
rather than cells. We must rather enlarge our conception 
of the cell from the morphological standpoint to include all 
protoplasmic masses enclosed by a continuous plasma-mem¬ 
brane. Physiologically it is the unit in nutrition, growth, 
irritability, and asexual reproduction, whether one- or many- 
nucleated. In sexual reproduction, on the other hand, the 
function of transmitting hereditary characters is probably to 
be attributed largely to the nucleus as an independent organ. 
The significance of multinucleated cells in the plant-economy 
is doubtless different under different conditions. After the 
cell has reached a certain size further growth makes distribu¬ 
tion of the nuclear material desirable in order that the nuclear 
activities may be represented equally in all its parts. In the 
hyphae of Sphaerotheca , on the other hand, whose cells contain 
one to several nuclei, this inequality and the multinucleated 
condition itself may be merely the result of the fact that 
a perfect correlation between the processes of nuclear and 
cell-division has not yet been attained. 
In the sexual cells of Py^onema^ as I have described them 
above, the multinucleated condition is plainly an advantage 
in insuring the simultaneous fertilization of large numbers of 
nuclei, and in the motility which is thus secured for relatively 
large masses of protoplasm. If the oogonium, for example, 
were uninucleated, a period of nuclear division would have to be 
interposed between fertilization and ascospore formation which 
is probably a much less favourable time for such processes 
than that prior to fertilization, when the numerous nuclei 
of the oogonium, as we have it, are produced. The condi¬ 
tions in Pyronema as compared with those in Nemalion , 
for example, may be regarded as intended to transfer the 
work of producing the numerous nuclei to be used in spore- 
