324 BOTANICAL GAZETTE [october 



published in Rhodora. Brainerd 



from 



It 



is the purpose of the present and succeeding articles to demonstrate 

 evidence from the morphological side that hybridism is extremely 

 widespread in nature, among the higher or angiospermous plants 

 in particular, and that there is every reason to suppose that it has 

 been an agency of great importance in multiplying species, although 

 it is logically inconceivable in the present state of our biological 

 knowledge that it could have presided at their origin. 



In the following paragraphs the general conditions of sporogeny, 

 so far as they are related to the matters under consideration, will 

 be discussed and compared in the main groups of the embryophytes. 



Beginning with the liverworts, the writer has examined a number 

 of examples from the Marchantiales, Anthocerotales, and Junger- 

 manniales (both acrogynous and anacrogynous), with the result 

 that in no case which has come under his observation are there 

 present any abnormal products in connection with spore-formation, 

 unless the elaters can be considered abnormal structures in this 

 respect. These elements, although undoubtedly derived from 

 potential spore mother cells, are perfectly normal and have no 

 significance in relation ta a possible genetical impurity, any more 

 than have the abortive spores and spore mothers found in the case 

 of heterospory. In Boschia, as is shown in Leitgeb's classic mono- 

 graph, the elaters are represented by sterile cells without tracheary 

 thickenings. In Sphaerocarpus the multinucleate condition of the 

 elateriform cells clearly reveals their morphological derivation from 

 spore mother cells. Fig. i illustrates the condition of the spores 

 in Marchantia polymorpha, as an example of the liverworts. The 

 elaters and spores are clearly seen, the former as spirally thickened 

 bands, and the latter as dark or lighter spherical bodies. Where 

 the spores are light in hue, the plane of section does not include 

 the protoplasmic contents. Whether light or dark, the spores are 

 of equal size and unshrunken. 



An examination has been made of the sporogonia of a consider- 

 able number of the leafy mosses, with results, as far as they have 

 gone, similar to those presented by the liverworts. The only 

 genus examined which showed imperfect or abortive spores was 



