1902-1903-] Report of the Microscopical Section. 59 



REPORT OF THE MICROSCOPICAL SECTION. 

 By Mr JAMES RUSSELL, Convener. 



The attention of the members during the session was directed 

 to the study of the Pteridophyta or Vascular Cryptogams, the 

 object being to learn their morphology and follow their life- 

 history, and thus see their relationship phylogenetically to the 

 Phanerogams. This comparative mode of examination has 

 revealed the fact that between the Gymnosperms, as the more 

 lowly developed of the Phanerogams, and the Pteridophyta, as 

 the more highly developed of the Cryptogams, there is no 

 sharply defined barrier. The more advanced development of 

 the Phanerogams is limited to the sporophyte, while what has 

 been gained in this direction has been lost by the oophyte, 

 which has been reduced from an independent plant to a few 

 cells wholly dependent upon the sporophyte for their exist- 

 ence. In the genera studied the independent existence of the 

 oophyte, and thus the alternation of generations, was clearly 

 traceable, especially in the Filices. 



All the Phanerogams are heterosporous — that is, producing 

 spores of two kinds — while the first of the vascular cryptogams 

 studied, the Selaginella, is also heterosporous, and thus forms 

 a connecting-link between the Phanerogams and the Crypto- 

 gams. 



The Selaginella is a large genus, but there is only one 

 British species — Selaginella selaginoides. The species studied, 

 however, was Kraussiana, a native of South Africa, but culti- 

 vated in most greenhouses. It is a plant with a creeping 

 stem, which rises a few inches above the ground, and forks 

 repeatedly. At each bifurcation of the stem a colourless 

 root-like organ arises, called a rhizophore, which grows down- 

 wards and seeks the ground, on reaching which it branches 

 and forms rootlets. 



As has been said, it is heterosporous — that is, its fertile 

 spikes bear both microspores or male spores, and macro- 

 spores or female spores. The covering or sac in which the 

 microspores are produced is called the microsporangium, and 

 that in which the macrospores are produced the macrospor- 

 angium. Each microsporangium gives rise to a mass of 



