ABNORMALITIES OF THE LIFE-CYCLE 



[CH. 



to be widespread, and it has been shown how in certain cases they can be 

 artificially induced. Not only are the normal limits between the gameto- 

 phyte and the sporophyte broken down by such observations as these, but 

 the features of the two generations are liable to be mixed up in the most 

 perplexing fashion. 



In simple cases a succession of events, in themselves abnormal, may be 

 seen following with some degree of regularity. For instance, in Nephrodhun 

 pseudo-mas, var. cristatujii, Cropper, an apogamous production of a sporo- 

 phyte takes place, but soon aposporous prothalli are borne upon the margins 

 of its first leaves (Fig. 297). A similar collocation of apogamy and apospory 



Fig. 2 9 7 . Nephroduiiii pseiido- 

 mas,\&x.c?-isiaftif)i,Cvo])\)eY. 

 Drawing by Dr Lang, show- 

 ing apogamous transition 

 from prothallus to sporo- 

 phyte, and subsequent apo- 

 sporous transition from spo- 

 rophyte to prothallus at the 

 apex and margins of the leaf. 



Rr 



%fS^ 



^ 



b ' X n 



Fig. 298. Scolopendrhim viilgare. Prothallus from 

 the branched cylindrical process of which ten roots 

 arise: eight of these are visible in the drawing, 

 (x about 6.) (After Lang.) 



has been seen in a number of cases. Sometimes the parts of one or of the 

 other generation appear to be formed without any definite sequence. This 

 was made particularly plain by the cultures grown by Lang (1898), who 

 found numerous roots, without any corresponding leafy shoots, borne upon 

 prothalli of Scolopendi^mm (Fig. 298). Sporangia were seen to be borne upon 

 a process growing out from the prothallus of Nephrodiiim dilatatnm, while 

 numerous archegonia were seated on its base (Fig, 299). He even observed 

 young sporangia growing out from a transformed archegonium of Scolopen- 

 drium (Fig. 300). A similar medley of sporophytic and gametophytic features 

 was found by von Goebel (1908) in a regeneration-growth from the primor- 



