REPRODUCTION OF THE ZYGNEMACER. 433 
less abundant than the female filaments*. It follows that a 
large number of female filaments, or of cells in the female fila- 
ments, do not conjugate at all; in these the protoplasm and 
chlorophyll retain their originalform. Very rarely they contract 
into an apparent zygospore; but whether these were fertile I 
have had no opportunity of ascertaining. It is quite probable 
that parthenogenesis does sometimes take place. 
But if there is any real previous differentiation between the 
male and female filaments, it would probably manifest itself in 
some way or other in the cells themselves. De Bary (J. c. p. 4) 
states that in Spirogyra Heeriana there is a small but constant 
difference between the primordial utricles of the two conjugating 
cells—that of the active [male] cell being pear-shaped, with the 
narrow end projecting into the canal; that of the passive [female] 
cell nearly globular. This difference, however, could only be 
detected after contraction of the protoplasmic contents of the 
cells had taken place. I was led myself rather to expect a differ- 
entiation in respect to size. In the allied genus Strogonium 
Cleve (Quart. Journ. Mier. Sci. 1873, p. 131) describes two species, 
S. punctatum and S. stictitum (comprising the whole genus), iu 
which the female cell is distinctly longer than the male cell. 
The following observations and measurements refer to one or 
other of the numerous forms of one of the commonest species of 
Spirogyra, S. porticalis, Vauch., growing in a freshwater aquarium. 
Fig. 2. 
S. porticalis. Conjugating filaments, showing relative size of male (upper) and 
female (lower) cells. Xx 165. 
Assuming the active filaments, or those which empty them- 
selves of their contents, to be male, and those in which the zygo- 
Spores are formed to be female, I find a very common, if not inva- 
riable, difference both in the diameter of the filaments and in the 
length ofthe cells. Of a large number of measurements, which all 
* This may be compared with the much greater abundance of female than of 
male individuals in such dicecious water-plants as Anacharis, Vallisneria, Hydro- 
charis, &c. 
LINN. JOURN.—BOTANI, VOL. XX. 2N 
