402 



VASCULAR CRYPTOGAMS. 



transformed into a mass of tissue consisting of but few cells. One of these cells 

 remains sterile, and may be considered a rudimentary prothallium ; while from the 

 others originate the mother-cells of the antherozoids, and these may therefore be 

 looked on as a rudimentary antheridium. 



The microspore of Isoetes laaistris breaks up, after hibernation, into a very 

 small sterile cell and a large one comprising the whole of the rest of the contents 

 (Fig. 301 A — C). The former {v), cut off by a firm wall of cellulose, does not 

 undergo any further considerable changes ; the latter, on the other hand, splits up 

 into four primordial cells without cell-walls, of which the two ventral ones produce 

 each two antherozoid-mother-cells, and therefore four in all. Pfefifer has confirmed 

 the statements of Millardet that in Selaginella, long before the spores escape from 

 the sporangium, a small sterile cell is first of all separated by a firm wall, while the 

 other large cell breaks up into a number (6 to 8) of primordial cells (Fig. 303 A — D). 

 He found, however, their arrangement different in Selaginella Mariensii and caulescens 

 from that which Millardet described in the case of 6". Kraussi'ana, a variation which 

 seems immaterial when compared with similar differences in the antheridium 



Fig. 202.— Isoetes lacustris (after Hofmeister) ; A macrospore, two weeks after its escape from the sporangiuin, rendered 

 transparent by glycerine (X6o) ; R longitudinal section of the prothallium four weeks after the escape of the macrospore, 

 a archegonium (X40). 



of Ferns. The essential difference between the results of the two observers con- 

 sists in this : — that, according to Millardet, only two of the primordial cells produce 

 the mother-cells of the antherozoids, which then, increasing in number, cause the 

 absorption of the rest of the primordial cells, and fill up the spore; while Pfeffer found, 

 in his species, that all the primordial cells underwent further division, and con- 

 tributed to the formation of the antherozoids. As to the latter they were both 

 in accordance. In Isoetes the antherozoids are long and slender, attenuated, and 

 splitting up at both ends into a tuft of long slender cilia; in Selaginella they are 

 shorter, thick behind, finely drawn out in front, and divided there into two long 

 fine cilia. In the perfectly mature condition the antherozoids are rolled up into an 

 elongated helix or into a short spiral. The mode of their formation in the mother- 

 cells is the same in both genera, and agrees in essential points with that of Ferns. 

 A cell-nucleus is not present at the time when the antherozoid is first formed ; the 

 contents of the cell are perfectly homogeneous ; the antherozoid originates from a 

 shining scarcely granular mass of protoplasm which encloses a vacuole, the cilia 

 at one end being formed first, and the spiral body becoming differentiated from 

 before backwards by a kind of splitting of the protoplasm. The antherozoid is 



