20 Veir Brecuer WITTROCK. 
formed immediately at the germination of the spore, thus forms a sharp 
limit between the cauloid and rhizoid of the thallus. ’) 
Before quitting the germination in order to pass to an account of the 
increase and development of the two constituent parts of the thallus, formed 
in the manner now described, it may seem fit to account for the deviations 
from the regular proceeding which may occur in the germination of the 
spores. I have found deviations of two kinds. The first deviation con- 
sists in the following fact: one of the two processes, which the spore 
sends forth in germinating, remains very small; besides, no transversal 
wall in the spore is developed. The process, of which the increase 
ceases at so early a period, is, as to its situation, analogous with the 
process which does; in a normal germination, give rise to the rhizoid; 
and it is therefore to be regarded as a rhizoid in a rudimentary state. 
This rhizoid will thus consist not of a whole cell, but only of a process, 
pointing downwards, from the basal cell of the plant, otherwise belonging 
to the cauloid. (Such rhizoids I have found now and then in P. kewensis 
nob. (pl. 1, fig. 8 rh, and pl. 4, fig. 2, 3 rh) and.in P. Cleveana nob- 
(pl. 4, fig. 13 rh), and often in P. equalis nob. (pl. 1, fig. 5 rh). The 
first transversal parting wall which is formed in a germination of this 
kind, will be placed in the cauloid a considerable space above the ger- 
minated spore (pl. 4, fig. 3, 13 w). No transversal wall being formed in 
the spore (as is mentioned above), it will not be possible to distinguish 
any sharp limit between the cauloid and the rudimentary rhizoid. Of 
P. Cleveana nob. I have, however, found one specimen, the one repre- 
sented pl. 4, fig. 14, which has a parting wall, w, though imperfect, 
between the cauloid and the rudimentary rhizoid. This specimen does, 
moreover, show the peculiarity that a new basal spore is formed, within 
the membrane of the original germinated spore, by the lowest cell of 
the cauloid (see regarding this m the preceding paragraph page 15). — 
The second deviation consists in the following process: the spore, in the 
germination, instead of sending forth two diametrically opposite pro- 
cesses, only sends forth one, which by its further development gives 
1) In general it is very easy even in fully developed specimens to see which 
is the transversal cell-wall developed at the germination of the spore, and thus to 
identify with certainty the limit between the rhizoid and cauloid; but now and then 
we may meet with some difficulties. Thus it would be very difficult, in the specimen 
of P. Cleveana nob. represented pl. 4, fig. 18, to decide with certainty whether the 
cell-wall marked w’ or the one marked ww” is the one first formed. For my part 
I think it most probable, that the one marked w’ is the primary one; in which case 
all that is situated below it would belong to the rhizoid. 
