410 Morphologie und Teratologie. 



L'auteur a verifie que le Fusarium Solani, cultive dans Line 

 maceration de Pomme de terre sucree, amene un abaissement 

 du point de congelation de ce milieu, par consequent Line 

 augmentation de sa concentration. Paul Vuillemin. 



BOWER, F. 0., Studies in the Morphology of Spore- 

 producing Members. No. V. General Compari- 

 sons, and Conclusion. (Proc. Royal. Soc. LXXI. 

 Read February 12, 1903. p. 258—264.) 



This concluding Memoir contains a general discussion of 

 the results acquired in the four previous parts of this series, 

 and of their bearing on a theory of Sterilisation in the sporo- 

 phyte. The attempt is made to build up the comparative mor- 

 phology of the sporophyte from below, by the study of its simpler 

 types; the higher and more specialised types are left out of 

 account, except for occasional comparison. It is assumed for 

 the purposes of the discussion that alternation of generations in 

 the Archegoniatae was of the antithetic type, and that apogamy 

 and apospory are abnormalities, not of primary origin. 



After a brief allusion to facts of Sterilisation in the Sporo- 

 gonia of Bryophytes the similar facts are summarised for the 

 Pteridophytes. It has been found that examples of Sterilisation 

 of potentially sporogenous cells are common also in vascular 

 plants, while occasionally cells which are normally sterile may 

 develop spores. Hence it is concluded that spore production in 

 the Archegoniate plants is not in all cases strictly limited to, or 

 defined by, preordained formative cells, or cell-groups. A dis- 

 cussion of the archesporium follows, and though it is found that 

 in all Pterldophyta the sporogenous tissue is ultimately re- 

 ferable to the segmentation of a superficial cell, or cells, still 

 in them, and, indeed, in vascular plants at large, the segmen- 

 tations which lead up to the formation of spore-mother-cells 

 are not comparable in all cases; in fact, that there is no 

 general law of segmentation underlying the existence of that 

 cell or cells which a last analysis may mark out as the „arche- 

 sporium"; nor do these ultimate parent cells give rise in all 

 cases to cognate products. Therefore it is concluded that the 

 general application of a definite term to those ultimate parent 

 cells which the analysis discloses has no scientific meaning, 

 beyond the statement of the histiogenic fact. 



Further, it is shown that the tapetum is not a morpho- 

 logical constant, but varies both in occurrence and origin; that 

 even the individuality of the sporangium is not always main- 

 tained. All that remains then as the fundamental concep- 

 tion of the sporangium in vascular plants is the spore- 

 mother-cell, or cells, and the tissue which Covers them in, 

 for such cells are always produced internally. The definition 

 of the sporangium may then be given thus: „Wherever we find 

 in vascular plants a single spore-mother-cell, or connected 



