818 
THE ZYGNEMACEiE. 
the protoplasm is never fluid in the physical sense of the 
word.” When complete union of the two cell masses, 
accompanied by further contraction and expulsion of water 
(Sachs), has taken place, the united body assumes its specific 
form and begins to elaborate its protective envelope. This is 
composed of three layers, the innermost of which only— 
being the true spore membrane—is concerned in the after 
germination of the spore; the other two forming a merely 
protective shell. When all is perfected, this body—the result 
of the union of the contents of two cells—is termed a 
Zygospore. This is the equivalent of the seed in the higher 
plants : like the seed, the zygospore has enduring vital power; 
it can survive the lapse of time, extremes of temperature, and 
so forth. As this body matures its contents become brown, 
homogeneous, and refractive ; a conversion of its endochrome 
into oily matter apparently takes place. When germination 
begins the oily matter disappears or is reconverted into green 
granular matter; this soon assumes a spiral form which 
becomes more distinguishable with the lengthening of the 
cell. 
After some months of rest—and in its proper time, the 
conditions being favourable—the zygospore begins to ger¬ 
minate. The inner and stouter of the two layers of its 
protective shell, or envelope, dehisces by a longitudinal 
sinuous fissure in all those having an ovoid form ; the young 
plant—the future filament—then bursts through the outer 
layer and emerges as an elongate claviform body attached by 
its thin end to its envelope. It grows rapidly, cell division 
commences, and soon it assumes the form of, and ultimately 
grows into a free filament like those from which it sprang. 
With the germination of the zygospore the life cycle is 
completed ; the empty shell—together with its parent cells— 
having fulfilled its office, now speedily decays. It does not 
always follow that the zygospore is formed in the germ-cell. 
In some species of Zygnema, in Mougeotia, and in Alesocarpus , 
it is formed in the middle of the conjugating canal; whilst 
in Staurospermuin it is a cruciate, or a four or more angled 
body, occupying the whole of that space. 
The three typical forms of conjugation in this family are : 
the scalariform, the lateral , and the genujiexuous. In the first 
the entire series of cells of each of two parallel filaments 
usually take part in the process; there results a ladder-like 
body, the two filaments representing the side pieces, and the 
transverse conjugating canals the rounds. This is the most 
common form, and here the zygospore is always formed in 
the germ-cell. 
