1895.J Morphology of Spore-producing Member, 



139 



I. Oph. vulgatum, L.," Moscow, 1892). On looking more care- 

 fully into this question, however, I have found that a band of super- 

 ficial cells, differing in origin and segmentation from the surrounding- 

 cells, may be recognised as the spor angiogenic hand ; this gives rise 

 to the sterile septa, the sporogenous groups, and the external wall of 

 the sporangia ; the band usually consists of two longitudinal rows of 

 cells, possibly referable in origin to a single row, but there is some 

 variety of detail. The observations have been made on three species, 

 viz., 0. vulgatum. L., 0. reticulatum, L., and 0. pendulum, L. 



The band, at first undifferentiated, subsequently forms (i) arche- 

 sporia at intervals, (ii) sterile septa which intervene between them, 

 and (iii) the outer sporangial walls. The cell-groups which give rise 

 to septa and to archesporia are sister cell-groups, having a common 

 origin, and no difference can be seen between them in early stages ; 

 the distinction only becomes apparent as the archesporia attain their 

 characteristic denser contents, and the difference is thus functional, 

 not genetic. The archesporium of the single sporangium has not 

 been found to be referable in origin to a single cell, and it is not 

 defined by the first periclinal wall of the cells of the sporangiogenic 

 band. These facts are all compatible with a theory of the origin of 

 the spike of Qphioglossum by septation from a simple sporangium of 

 the Lycopodinous type, and the sporangiogenic band may be compared 

 with the band of cells, sometimes a single row, or two or three, 

 which, after periclinal division, give rise to the archesporium of 

 Lycopodium. 



The development of the sporangia of Botrycliium and Helmintho- 

 stachys has also been traced, but these facts do not bear so directly 

 upon the question of the nature and origin of the Ophioglossaceous 

 spike as those derived from the study of Ophioglossum. 



Abnormalities have played a large part in former discussions upon 

 the morphology of the spike in the Ophioglossacea3. While recognis- 

 ing the obvious correlation which exists between vegetative develop- 

 ment and spore-production, it has been concluded that the abnor- 

 malities in this family do not form a sufficient basis for argument, 

 certainly not when the conclusions drawn from them are in opposi- 

 tion to the results of comparison of normal specimens. Such com- 

 parison led Mettenius, Strasburger, Celakovsky, and others to 

 recognise a relationship of the Ophioglossacese to the Lycopods. 

 This comparison has been developed at considerable length, on 

 grounds not only of the similarity of the development and position 

 of their spore-bearing members, but also by comparison of the 

 synangia of the Psilotacese ; the Grametophyte, also, and sexual 

 organs and embryology, as far as known, have been taken into 

 account, and a detailed comparison made of certain features in the 

 anatomy of the Lycopods and Ophioglossaceas. From these various 



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