47© VASCULAR CRYPTOGAMS. 



each two antherozoid-mother-cells, and therefore four in all. Pfeffer 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. 331 A — D). 

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

 from that which Millardet described in the case of S. Kraussiana, a variation which 

 seems immaterial when compared with similar differences in the antheridium 

 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 mode of development 

 of the antherozoids 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 



Fig. j,y:i.—Isoetes lacustris (after Hofmeister) ; A inacrospore, two weeks after its escape from the sporangium, rendered 

 transparent by glycerine (X 60) ; B longitudinal section of the prothalliuin four weeks after the escape of the macrospore, 

 a archegonium (X 40)- 



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 homo- 

 geneous ; 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 split- 

 ting of the protoplasm. The antherozoid is originally curved spirally round the 

 central vacuole ; this latter, surrounded by a fine membrane, not unfrequently 

 remains attached to the posterior end of the antherozoid after it has escaped, and 

 is carried along by it. The movement does not last longer than five minutes in 

 the antherozoids of Isoetes^ in Selaginella from one-half to three-quarters of an 

 hour. From the commencement of germination till the complete maturity of the 

 antherozoids there is, in Isoetes, an interval of about three weeks ; the same period 

 from the dissemination of the spores is necessary in Selaginella. 



The Macrospores produce the female prothallium, which is an endogenous struc- 

 ture in a still higher degree even than is the case in the Rhizocarps. In this respect 



