96 



Prof. F. 0. Bower. 



" Studies in the Morphology of Spore-producing Members. IV. 

 The Leptosporangiate Ferns." By F. 0. Bower, Sc.D., F.E.S., 

 Regius Professor of Botany in the University of Glasgow. 

 Received April 6 —Read April 20, 1899. 



(Abstract.) 



The characters used in current classifications of Ferns need streng- 

 thening. In recent years the more detailed knowledge of the prothallus 

 has been used for this purpose, but while not denying its value in 

 certain specific cases, the author holds that the vegetative development 

 of the prothallus is an uncertain guide to a general classification. On 

 the other hand the archegonium is so uniform in its character that it 

 gives little help ; the comparison of the antheridium is, however, a 

 useful aid, though not sufficiently varied to serve in detail.* Accord- 

 ingly the sporophyte must be the main basis. Its vegetative organs 

 have lately been largely used for systematic purposes by Christ ;f but 

 the same objection holds here as in Phanerogams to the use of these 

 as characters of first rank for comparison. An attempt has therefore 

 been made in this memoir to strengthen the characters derived from 

 the sorus by a fresh examination of its details, and certain of its 

 features will now be used for purposes of general comparison, which 

 have hitherto received too little attention ; they are : — 



1. The relative time of appearance of sporangia of the same sorus. 



2. Certain details of structure of the sporangium, including its stalk. 



3. The orientation of the sporangia relatively to the whole sorus. 



4. The potential productiveness of the sporangium as estimated by 



its spore-mother cells, and the actual spore-output. 



Observations of these features extending over all the more important 

 living genera, coupled with data of habit and the characters of the 

 Gametophyte as collateral evidence, have led the author to divide the 

 homosporous Ferns thus : — 



Marattiacese Eusporangiate 

 Osmundacege 

 Schizaeacese 

 Gleicheniacese 

 Matonineae 

 Loxsomaceae 



Hymenophyllaceae J- Leptosporangiate 

 Gradatae i Cyatheaceae 

 Dicksonieaa 

 Dennstaedtiinae 

 The bulk of the 

 Polypocliaceae 



* Heim, < Flora/ 1896, p. 355, &c. 

 f 1 Die Farrnkriiuter der Erde,' Jena, 1897. 



Simplices 



Mixtae 



