J24 



MOSSES AND FERNS 



CHAP. 



more above the surface. The spermatozoids are described as 

 similar to those of the Polypodiacese, but half as large again. 



The writer has succeeded in securing the earliest phases of 

 germination in two other species, viz. Ophioglossuni (^Ophioderina) 

 pendulum and Botrychimn Virginia^tuni, as well as the older 

 prothallia of the latter. The germination in both cases is 

 extremely slow, especially in the former, where a year and a 

 half after the spores were sown the largest prothallia had but 



three cells. Probably under natural con- 

 ditions the growth is more rapid. The 

 spores of both forms show much the same 

 structure. The tetrahedral spores contain 

 granular matter, with numerous oil -drops, 

 and a central large and distinct nucleus. 

 The exospore is colourless, and upon the 

 outside presents a pitted appearance in 

 Ophioglossuni, and irregular small tubercles 

 in Botrychiuni. The perinium or epispore 

 is not clearly distinguishable from the 

 exospore. In both cases chlorophyll is 

 absent in the ripe spore. The first sign of 

 germination is the absorption of water and 

 splitting of the exospore along the three 

 radiating lines on the ventral surface of the 

 spore. The spore enlarges considerably 

 before any divisions occur, but remains 

 globular in form, and no chlorophyll can 

 be detected. In this condition, which was 

 observed within two weeks after the spores 

 were sown in Ophioglossuni, it may remain 

 for several months unchanged. The first division wall is usually 

 at right angles to the axis of the spore, and divides it into two 

 nearly equal cells, of which the lower has more of the granular 

 contents than the upper one. The endospore is noticeably 

 thickened where it protrudes through the ruptured exospore. 

 The next wall, in all cases observed, is at right angles to the 

 first, and always in the lower cell, which it divides into equal 

 parts (Figs. 1 09, I I o). In Botrychiuni at this stage a few 

 large chloroplasts were seen in both upper and lower cells, but 

 Ophioglossuni showed no positive evidence of chlorophyll, 

 although it seemed sometimes as if a faint trace of chlorophyll 



Fig. 109. — Germinating spore 

 of Ophioglossuni (Ophio- 

 derjiid) pendulum (L.)- 

 A, Surface view ; B, 

 optical section, x 600. 



