INTRODUCTION. 
substance with it. The size of the antherozoids is so inconsiderable that they 
scarcely add appreciably to the mass of the oosphere, but yet produce a change in 
it, one consequence of which is that it becomes invested with a firm cell-wall, and 
then constitutes the Oospore. 
The oospore may germinate immediately and give rise to a plant resembling the 
mother-plant, as in Fucus, or only after a certain period of rest like the zygospores, 
and this is the usual case. But here again the oospore may on germination give 
rise directly to a plant resembling the mother-plant, as in Vaucheria and some 
Saprolegnieae ; or it may, after remaining dormant, produce out of its contents a 
larger or smaller number of zoospores, each of which finally gives rise to a plant 
like the mother-plant, as in Sphceroplea, (Edogonium, and Cystopiis. In this process 
a rudimentary alternation of generations can again be detected:— an oospore which 
breaks up into zoospores may be compared to the sporogonium of a Moss in 
Fig. i6j. —Examples of the production of oospores; A in Gidogoniwn ; B m. Saprolegnia 
(after Prin^srsheim) ; og oogonium; o oosphere; a antheridium ; rn small male plant or dwarf 
male ; s antherozoid. 
which all the parts except the spores are suppressed. If we were to imagine the 
fertilised oosphere in the archegonium of a Moss as itself producing the mother- 
cells of the spores\ we should have something similar to one of these oospores. 
In this case therefore the oospore is properly a many-spored fructification in 
the same sense as the Moss-capsule ; the zoospores produced from it are true 
spores in the sense of those of Muscinese and Ferns, and we have consequently 
the first indication of the alternation of generations which attains its highest 
development in those classes. The new plants which result from the direct 
germination of the oospores, or through the medium of zoospores, have the power, 
in most cases, of propagating non-sexually by the formation of gonidia, until at 
length individuals arise which produce antheridia and oogonia. This non-sexual 
reproduction may be compared to that of the Marchantieae by gemmae produced 
on their vegetative body, until finally antheridia and archegonia are developed. 
^ That such an analogy is not altogether fanciful is shown by Riccia, a genus of Hepaticae, 
the extremely simple sporocarp of which may well be compared to the oospore of an CEdogonium. 
Pringsheim and De Eary have already pointed out this analogy (see De Bary, Die Familie dtr 
Conjugaten, Leipzig 1858, p. 60). 
