110 SPORES ANALOGOUS TO POLLEN. [BOOK i. 



months after the destruction of the pistillum. It is scarcely 

 necessary to ask, how it is possible that the sporules can be 

 impregnated before the theca, in which they are developed, 

 is in existence. If sexes are to be found in Mosses, they 

 must be sought in the theca ; and accordingly we find that 

 various botanists, probably impressed with this idea, have 

 named in succession all the different parts of this organ as 

 performing the function of the anthers. Some have fixed on 

 the columella ; others on the peristome ; others on the oper- 

 culum. It is altogether unnecessary to enter on an exami- 

 nation of the truth of these various hypotheses, as their 

 original proposers have adduced so little in their support, 

 that no one at present considers them worth the slightest 

 attention." (Linncean Transactions, vol. xvii.) 



Mr. Valentine not only thus disproves the possibility of 

 the parts called Sexes in Urn-mosses being so ; but supports 

 the opinion of Mohl that their sporules, and he adds those of 

 all cellular plants, are analogous to the pollen of the Vas- 

 culares, slightly modified by circumstances, but agreeing in 

 every essential particular. 



" The analogy of the development of the sporules to that 

 of pollen is very striking," he observes, " even to a superficial 

 observer, and has not escaped the notice of botanists. A sec- 

 tion of the anther of the common garden variety of Primula 

 vulgaris, taken from a bud when about the size of a small 

 pin's head, exhibits a structure which may be compared to a 

 section of the theca of Polytrichum. In the former we find 

 an axis of dense tissue (the connectivum) surrounded by the 

 cuticle. This axis is not central, but placed nearer to the 

 cuticle, on the back of the anther, and may be considered as 

 the columella, whilst the cuticle will represent the theca. 

 A separation of the tissue gradually takes place, in four dis- 

 tinct points, nearly at equal distances from the axis. As the 

 axis is not centrical, these points lie towards the front of the 

 anther. Between each of these points the cuticle is fur- 

 rowed longitudinally, so that the section has somewhat of a 

 quadrangular figure. The theca of Polytrichum merely differs 

 from this in having a complete separation of its tissue all 

 round the axis, instead of in four points only. The spaces 



