XV S UMMA RY AND CONCL USIONS 5 1 3 



similar to the primary vascular bundles in the embryo of 

 the Pteridophytes, and in all probability is to be regarded 

 as its homologue. This central strand of conducting tissue, 

 together with the massive assimilative tissue system of the 

 larger species of Anthoceros, would make the sporogonium 

 independent of the gametophyte, were a root or some similar 

 structure present by which it could be connected with the 

 earth. The alternation of sporogenous and sterile cells in the 

 archesporium, by which the latter is divided into imperfect 

 chambers containing the spores, is, perhaps, the first indication 

 of the separate sporangia of the Pteridophytes. The most 

 striking difference, then, between the sporogonium of Anthoceros 

 and the sporophyte of the simpler Pteridophytes, such as 

 Ophioglossiun and Phylloglossuin, aside from the absence of 

 roots, which are, physiologically, replaced by the massive foot, 

 is the absence of a definite axis with its lateral appendages 

 (leaves) and sporangia. In Anthocei'os the assimilative tissue 

 forms a uniform layer over the whole upper portion of the 

 sporophyte, instead of being restricted mainly to the special 

 organs of assimilation or leaves, and the archesporium is 

 continuous instead of being divided into definite sporangia. 



Many attempts have been made to explain the origin of 

 the leafy axis of the sporophyte of the vascular Archegoniates 

 from the Bryophyte sporogonium. The latest theory is that 

 of Professor Bower,^ who has brought forward much important 

 evidence to show that the simpler strobiloid Pteridophytes, 

 especially Phylloglossuin, are the primitive forms from which 

 the others have sprung. His conclusions are based largely 

 upon a comparison of Phylloglossuni with the embryonic con- 

 dition of Lycopodiuni, where the long dependence of the 

 embryo upon the prothallium, the rudimentary vascular 

 bundles, and the late appearance of the root are very striking, 

 and certainly indicate a very low rank for these forms in the 

 pteridophytic series. Another evidence of the close relation 

 of the Lycopodineae to the Bryophytes is the character of the 

 spermatozoids, which closely resemble those of the Liverworts, 

 both in their small size and the two cilia. Professor Bower's 

 theory as to the origin of the sporophytes is that these arose 

 " by a process of eruption from a hitherto smooth surface." 

 In this way he conceives that the smooth cylindrical sporo- 



^ Bower (16). 

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