20 



Veit Brecher 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. (pi. 1, fig. 8 rA, and pi. 4, fig. 2, 3 rh) and in P. Cleveana nob. 

 (pi. 4, fig. 13 rA), and often in P. cequalis nob. (pi. 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 (pi. 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 pi. 4, fig. 14, which has a parting wall, 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 in 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 



*) 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 pi. 4, fig. 18, to decide with certainty whether the 

 cell-wall marked w' or the one marked tv" 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. 



