THE CLUB-MOSSES 



185 



alent to a proportion of 125,000 to 1 in bulk. 

 The megaspores were commonly about one milli- 

 metre in diameter, and in some cones of Sigil- 

 laria they were double that size; the head of 

 a pin gives an idea of their average dimensions. 

 Megaspores are extremely 

 abundant in some kinds of 

 coal. 



Very commonly the mega- 

 spores were covered with 

 bristles, among which we 

 often find the microspores 

 entangled; this may have 

 been a means of ensuring 

 that the two kinds of spores 

 germinated together. Fig. 21. (A) Lepido- 



In some favourable cases " ron VeUhdmianum 



. . Megaspore failed with 



the preservation is so good the prpthallus, x 25; 



that the prothallus is Still (B) archegonium from 



, . . . another prothallus of the 



found within the megaspore same plant, x 140; (C) 



(see fig. 21, A). It consisted archegonium of Iso'etes, 



1 for comparison, after 



of a uniform, large-celled Hofmeister, x 200. A 



tissue, except on the side ^ d B from drawings by 



Mrs. D. H. Scott. 

 where the megaspore opened; 



here the cells were smaller, and Mr. W. T. Gordon 

 has recently been so fortunate as to discover a 

 well-preserved archegonium in this position (see 

 fig. 21, B). All the parts are shown the neck, 

 the canal, and the egg-cell; the agreement with 



