470 
VASCULAR CRYPTOGAMS. 
each two antherozoid-mother-cells, and therefore four in all. Pfeffer has confirmed 
the statements of Millardet that in Se/aginella, 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 ^. 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. 330. — Isoetes (after Hofmeister) ; A inacrospore, two weeks after its escape from the sporangium, rendered 
transparent by glycerine (X 60) ; 5 longitudinal section of the prothallium four weeks after the escape of the macrospore, 
a archegonium (X 4o)- 
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 
