APOGAMY 



53 



found, either showing normal struchire or various modifications of it. But 

 in other cases, which have been described in detail by Lang, 1 the 

 apogamous developments may diverge far from the normal in point of 

 the number and position of the parts. Originating by direct vegetative 

 growth from the tissues of the thallus, in place of the normal sequence 

 and position of the parts the several constituents of the sporophyte, root, 

 leaf, sporangium, may appear without order or numerical rule : ten or 

 more roots have been found apoga- 

 mously produced upon a prothallus 

 without other parts of the sporophyte 

 (Fig. 34) : sporangia have been ob- 

 served without sporophylls, originating 

 directly from a formless mass of 

 sporophytic tissue apogamously pro- 

 duced on the prothallus (Fig. 35), 

 or even, in an extreme case, from 

 the prothalloid cells of the archegonial 

 wall (Fig. 36). The irregularity of 

 such growths must be taken into 

 consideration in their theoretical 

 interpretation, as will be seen later. 

 Among the Archegoniatae apogamy 

 has hitherto been observed in a score 

 or more of species of Ferns, belonging 

 to the Osmundaceae, the Hymeno- 

 phyllaceae, and chiefly to the Poly- 

 podiaceae ; and examples are also 

 recorded from the Marsiliaceae. In 

 the Bryophytes, the Lycopodiales, 

 and the Equisetales no cases are as 

 yet recorded. It may be noted, how- 

 ever, that similar phenomena have 

 been observed in Flowering Plants, 

 such as AkhcmiUa, Thalictrum, 

 Antennaria, and Taraxacum? 



Turning now to Apospory, 3 that is, the transition by direct vegetative 

 growth from the sporophyte to the gametophyte without the intervention 

 of spores, instances are recorded from the Liverworts (Anthoceros, Lang), 4 

 from the Mosses (Hypnum and Bryum, Pringsheim, 5 Ceratodon, Stahl, G 



1 Phil. Trans., vol. cxc. (1898), p. 187, etc. 



2 For references see Strasburger, Flora, 1907, p. 139. 



y The term " Apospory ; ' was introduced by Vines, in an article on the " Proembryo 

 of Chara," Journal of Botany, 1878, p. 355. 



4 Annals of Botany, vol. xv., 1901, p. 503. * Pringsh. Jahrb., xi., 1877. 



*Bot. Zeit., 1876, p. 689. 



FIG. 35. 



Nephrodium dilatatum, Desv., var. cristatum 

 gracile. Prothalloid cylindrical process, bearing 

 archegonia near its base. It arises by the side of an 

 imperfect sporangium (sfi), and bears a similar 

 sporangium (sp) on the other side, and on the tip are 

 a number of sporangia associated with ramenta. 

 X 3 5. (After Lang.) 



