SEXUAL REPRODUCTION OF THALLOPHYTES, 3809 
a book which has been justly called classical, and which gives 
us the same pleasure in reading it that is to be found in the 
first account of the exploration of some entirely new country. 
It is worth while quoting a few sentences from Vaucher, 
because they illustrate very admirably the advantage of 
patience and persistence in this kind of study. 
“T had one day,” he says, ‘collected a considerable 
quantity of these plants, and, as was my practice, I was 
examining them rather asa matter of habit and rule than 
from the hope of finding anything new. I witnessed, how- 
ever, a phenomenon as novel as it was unexpected. On all 
the segments of the cylindrical tube small swellings or 
papille, irregular in form and mostly obtuse, made their 
appearance. Each gradually elongated itself till it met a 
papilla of the other conjugating filament” (p. 43). Since this 
time conjugation has been observed to take place with dif- 
ferences in detail in other genera. 
The conjugation is either effected transversely between the 
cells of different filaments (fig. 7 B), or longitudinally between 
adjacent cells of the same filament asin Rhynchonema and 
Pleurocarpus. In such genera as Mesocarpus and Pleuro- 
carpus the zygospore is formed between the conjugating cells, 
while in Zygnema, Spirogyra and Rhynchonema the zygo- 
spore is formed in one of the conjugating cells (fig. 7c). ‘This 
may be regarded as the commencement of a differentiation 
which leads eventually to the type of reproduction charac- 
teristic of the Oosporec. 
Fig. 7.—Conjugation of Spirogyra quinina (after Kutzing), 
Amongst Fungi a similar mode of conjugation has been 
observed to that in Mesocarpus. The first instance in which 
it was observed was by Ehrenberg (1829), in Sporodinia 
(Syzygites) ; the other instances in which it is known are 
Rhizopus (De Bary, 1866), Mucor fusiger (Tulasne, 1866), 
M. Mucedo and Phycomyces (Van 'Tieghem and Le Monnier, 
1872), Chetocladium and Piptocephalis (Brefeld, 1872). 
