XIV 



L YCOPODINE.'E 485 



The cells composing the septa arc narrow tabular ones, with 

 firm woody walls marked by numerous pits. Occasionally the 

 septum is partially absent and the loculi are thus thrown more 

 or less completely into communication. The spores are usually 

 of the bilateral form, like the microspores of Isoetes, but may 

 also be of the tetrahedral type. 



Bower regards the whole synangium as homologous with 

 the single sporangium of Lycopodiuni, and also calls attention 

 to its resemblance to the sporangium of Lepidodetidron, with 

 which the Psilotaceae also show remarkable resemblances in the 

 structure of the stem. 



TJie Selannelle(2 



'i>' 



Unlike the Filicineae, the heterosporous Lycopodineae out- 

 number very much the homosporous forms, but all of the 

 former may be reduced to a single genus, Selaginella, which 

 contains nearly three hundred and fifty species, and, except for 

 the presence of heterospory, approaches closely the genus 

 Lycopodiuin, to which it is clearly not very distantly related. 

 The great majority of the species of Selaginella belong to the 

 Tropics, and form a characteristic feature of the forest vegeta- 

 tion of those regions. A few belong to the more temperate 

 parts of Europe and America, and a small number, e.g. S. 

 rupeslris, S. lepidopJiylla, grow in dry situations. 



r 



TJie Ganietophyte 



Hofmeister ^ included Selaginella among the other Pterido- 

 phytes he studied, but he was unable to make out the earlier 

 stages of development of the prothallium. Later Millardet ' 

 and Pfeffer ^ made further investigations upon the same subject, 

 and added much to Hofmeister's account, but were also unable 

 to determine the earliest phases of germination. Belajeff^ has 

 since given a clear account of the germination of the micro- 

 spores, but up to the present time the exact method of formation 

 of the female prothallium has remained doubtful. Recently a 

 further contribution has been made to the subject by Heinsen,^ 

 which, however, adds but little to our previous knowledge. The 



1 Hofmeister (i). ^ ]\iniardet (i). ^ pfgffer, W. (i). 



4 Belajeff(i). ^ E. Heinsen (i). 



