1893.] Morphology of Spore-producing Members. 



19 



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

 Preliminary Statement on the Equisetaceas and Psilo- 

 taceee." By F. 0. Bower, D.Sc., F.R.S., Regius Professor 

 of Botany in the University of Glasgow. Received 

 January 30, 1893. 



Still maintaining the same general views as were put forward in 

 my preliminary statement on the Lycopodiiia3 and Ophioglossaoeae 

 ('Rov. Soc. Proc.,' vol. 50, p. 265), I have now investigated other 

 types from among the Vascular Cryptogams as regards the develop- 

 ment of their spore-producing members. As some considerable time 

 must still elapse before these and other results can be laid in full 

 before the Society, a further preliminary statement will now be made 

 of the more important facts recently obtained. It is assumed that 

 readers will bear in mind the views pat forward in the paper above 

 quoted, as regards sterilisation of potential spore-producing tissue, 

 the possible partitioning of an originally continuous sporogenous mass 

 by bands of sterile tissue, and as regards the elaboration of external 

 form which may follow on such partitioning. This will be specially 

 necessary for the appreciation of the facts relating to the Psilotaceae. 



Taking first the Equisetaceee, the development of the sporangia has 

 been closely followed by Goebel (' Bot. Zeit.,' 1880-81) ; I find it, 

 however, difficult to accept his conclusions as to the hypodermal 

 origin of the archesporium. 



On following the early phases of development in Eq. arvense, the 

 sporangium is found to be eusporangiate, but the essential parts of 

 the sporangium may be traced in origin to a single superficial cell, 

 the cells adjoining this laterally contributing only to form the lateral 

 portions of the wall. The first division of this cell is periclinal : the 

 inner resulting cell forms only a part of the sporogenous tissue; the 

 outer cell undergoes further segmentation, first by anticlinal, then 

 by periclinal, walls, and the inner cells thus produced are added to the 

 sporogenous tissue, and take part in spore- formation. The archesporium 

 of Eq. arvense is thus shown to be not of hypodermal origin in the 

 strict sense ; the same appears to be the case in Eq. limosum. Similar 

 additions to the sporogenous tissue by early periclinal division of 

 superficial cells is commonly to be seen in Isoetes, and occasional cases, 

 which are difficult to explain in any other way, have been observed 

 in some species of Lycopodium. It would thus appear that Groebel's 

 generalisation, that in all the Vascular Cryptogams which he investi- 

 gated a hypodermal archesporium exists (' Bot. Zeit.,' 1880, p. 569), 

 cannot be retained in the strict sense. 



The tapetum is derived from the stries of cells immediately sur- 



C 2 



