ON THE IMPREGNATION OF VAUCHERIA SESSILIS. 291 
protrudes—a rostrate elongation on the side next the hornlet, in 
which a considerable accumulation of the cutaneous layer is gra- 
dually formed, until it becomes perfectly stuffed. At the same 
time the apex of the hornlet becomes colourless, and a separate 
and distinct cell formed therein, containing minute, colourless, 
rodlike bodies imbedded in mucus, amongst which an indistinct 
movement may be perceived. The sporangium is now ruptured 
at the rostrate point by the pressure of the accumulated cutane- 
ous layer, and a portion of that substance, in the form of a drop 
of mucus, emitted. Simultaneously the apex of the hornlet opens, 
and innumerable excessively minute rodlike corpuscles, about 
1-180" in size, issue forth, and enter the sporangium by conti- 
nuous struggles in an uninterrupted succession of assaults and 
retreats for the space of more than half an hour. ‘These cor- 
puscles appear to be precisely similar both in form and move- 
ments to the so-called sporidia of the Pyrenothee, as represented 
in plates 28 and 29 of Leighton’s Brit. Angiocarpous Lichens. 
This supposed genus of Lichens, Pyrenothea, is now universally 
admitted to constitute the spermogonia, or male organs, of Li- 
chens: as, for instance, Pyrenothea leucocephala, Fries ; of Le- 
cidea abietina, Ach.; Pyrenothea vermicellifera, Kunz; of Bia- 
tora luteola, Fries. Examples of these several plants will be found 
in Leighton’s ‘ Lichenes Britannici Exsiccati,’ Nos. 163, 164, 102, 
and 90. M. Pringsheim does not state whether, like the sper- 
matia of Lichens, these corpuscles of Vaucheria sessilis are sup- 
ported on articulated pedicels, or whether they are free; but as 
mention is made of a mass of mucus remaining in the cell at the 
apex of the hornlet, it is probable that they are so. (See the fig. 
in Tulasne’s Mem. passim.) The corpuscles which have not en- 
tered the sporangium, but in which motion has ceased, exhibit 
two cilia of unequal length. These appendages, so far as I am 
aware, have not been detected in the spermatia of Lichens. 
After impregnation thus effected, a laminated membrane is 
formed around the entire contents of the sporangium, which 
thus becomes developed into an independent embryonic or spore- 
cell. This cell becomes gradually colourless, with the exception 
of one or more dark brown spots, and is detached by the ,decay 
of the membrane of the sporangium. After about three months 
it suddenly reassumes its green colour, and germinates into a 
young Vaucheria, exactly resembling the parent plant. 
