West & West. — Observations on the Conjugatae. 51 
(Fig. 52), which has a considerable resemblance to the aplano- 
spore of some species of Gonatonema (e. g. G. notabile). Soon 
after the coalescence of the gametes the wall of the zygospore 
increases much in thickness. 
One case was noticed in which a solitary gamete in one 
filament was conjugating with one of a pair in another 
filament (Fig. 51). 
There is no perceptible sexual differentiation between these 
gametes, but owing to the fact that they are specially cut off, 
this family must be regarded as considerably removed from 
the other families of the Conjugatae, though it is not so highly 
specialized as the Mesocarpeae. 
Fam. III. — Desmidiaceae. 
The chromatophores in the Desmidiaceae are disposed 
more or less symmetrically in the two halves of the cell, 
either as central masses of chlorophyll arranged in relation 
to certain pyrenoids, or as parietal and somewhat pulvinate 
masses containing scattered pyrenoids. 
In some genera these pyrenoids are definite ; the majority 
of Cosmaria have either one or two in each semi-cell, and the 
great majority of Staurastra contain one large one in the 
centre of each semi-cell. In a paper published by Lutke- 
muller 1 entitled ‘ Beobachtungen liber die Chlorophyllkorper 
einiger Desmidiaceen ’ the author demonstrates the irregu- 
larity of the pyrenoids in certain species. No doubt many 
irregularities are to be found in most Desmids, but as 
a general rule we find the central pyrenoids very constant in 
character. One of the species mentioned by Lutkemuller as 
very variable in this respect is Cosmarium pyramidatum , 
normal specimens of which should contain two pyrenoids in 
each semi-cell. Our experience of this species confirms his 
observations, but we may add that in this respect it is the 
most variable species that we have yet examined. 
Oesterreich. Botan. Zeitschr., 43. Jahrg. 1893, No. 1. 
