396 Brown: Regeneration in Phegopteris polypodioides 



either in the younger or older stages of their gametophytic or 

 sporophytic life history and especially in the younger stages, does 

 not always react in the same way to the same environmental con- 

 ditions; but each has a sort of individualism which enables it to 

 react in the way best fitted for its particular needs. It seems very 

 probable that in this particular case regeneration is closely con- 

 nected with nutrition for the reason that the severed leaf was not 

 able to regenerate immediately another sporophyte, but could 

 produce a cellular mass which appeared to be a reversion to a 

 prothallus-like structure. This structure after rhizoids developed 

 gave rise, in an apogamous manner, first to structures intermediate 

 between leaves and prothallia; then, as the number of rhizoids in- 

 creased, enlarging the absorptive surface, which in turn increased 

 the amount of nourishment, true leaves were produced. The 

 first of these were the ordinary type of young sporophytic leaf but 

 later ones were much more primitive in character, due doubtless 

 to the lowered vitality of the prothallus-like structure. This 

 coincides with Goebel's (i, vol. 2, p. 42) views. He considers a 

 reversion to a juvenile form as being the result of unfavorable con- 

 ditions to which the plant is subjected. It is also in keeping with 

 the results obtained by Miss Kupfer (3, p. 229) in her experi- 

 ments, which indicated that at the time of cutting under normal 

 conditions reserve food was present in sufficient quantities to 

 initiate the first stages of regeneration. If this food was absent 

 and its formation prevented regeneration was prohibited. 



Such an explanation as this does not lose sight of the impor- 

 tance of the other factors so strongly emphasized by various 

 workers, for all these factors doubtless play an important part in 

 nutrition. 



Experimental data in this particular case are not extensive 

 enough to permit drawing conclusions as to which of the above 

 factors or groups of factors acting separately or together, was the 

 determining one. However, since an intimate relation exists be- 

 tween growth and regeneration and since growth is dependent 

 upon nutrition, it would seem as if some phase of nutrition must 

 be an important factor in regeneration, if not the most important 

 factor. 



