BOTRYDIACEE. 113 
of slightly coloured protoplasm. These zoospores conjugate in twos, 
sometimes several together. They come in contact by their ciliated 
ends, then come to touch laterally by the uncoloured portions, when 
the fusion of the conjugating zoospores takes place, immediately after 
which they present a cordate figure, and in the middle a colourless 
vacuole. Finally, the isospore thus originating becomes globular, the 
vacuole occupying the centre. 
If the zoospores be isolated before conjugation, they will in the end 
break up, without presenting any products capable of germination. 
The zoospores originating from red spores have a different figure, 
their posterior end being rounded, but they have otherwise the same 
structure, and behave in the same manner as the others. The red 
spores maintain their germinative power for years, but after two years 
their zoospores are languid, and offer a parthenogenesis of a peculiar 
kind. The red spores, if kept moist only, become nothing altered after 
weeks, whilst the green, under these circumstances, may directly 
germinate into vegetative plants. 
The isospores are at first globular, and capable of immediate germina- 
tion. They also present resting stages, the original form becoming 
modified. Soon after conjugation these are flattened, with irregular 
lateral boundaries, which become on the following day hexagonal. The 
membrane becomes thickened, and presents tuberculations at the 
margin, but no secondary membrane is formed. Brought upon damp 
earth, they soon become globular, and otherwise behave as ordinary 
igospores. 
In order to distinguish that which appertains to the cycle of alterna- 
tion of generations from the rest, the simple method is to start from the 
fertilized germ, and see what are the modifications which are essential 
in order to arrive again at the same reproductive process. In this case 
we have the isospore—it germinates—produce the vegetative plant, 
which needs neither to divide, nor produce a sexual zoospore, nor to 
become an ordinary zoosporange—it can directly produce spores. These 
close the first generation. The second oospore generation occurs in the 
germination of these spores in the form of sexual zoospores, which 
directly lead to the formation of the isospore—the limits of two genera- 
tions. All the rest are but phenomena of adaptation. 
“Thus, in nature, the vegetative plants in spring almost all become 
zoosporangia, and spread the growth over considerable areas. Zoospores 
which fall into the water are not lost; they acquire a double membrane, 
and lie dormant until they chance mechanically to arrive on moist soil. 
If drought sets in, the plasma retreats to the roots; if the earth be 
some time a little moist, the root cells become hypnospores, awaiting 
the rain in order to develop multitudes of zoospores; but if the earth 
becomes rapidly dried, the root cells remain unaltered, until a moistening 
excites the formation of zoospores. A great many of the root cells can 
manifestly accidentally reach the surface of the soil, and thus, according 
to the state of the moisture of the earth or of the air, sometimes ger- 
minate, sometimes become zoospores.’’ All this inthe spring. The hotter 
months favour the formation of spores, but at that time only the 
vegetative plants are mostly to be found, either undergoing cell division 
or spore formation, They can also furnish uniciliate zoospores without 
becoming modified into ordinary zoosporanges, 
Formation of ordinary zoospores may be accomplished in a fourfold 
way— 
1, From the vegetative plant. 
2. From the ordinary zoosporange. 
8. From the root cell. 
4, From the hypnosporange. 
