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are merely amplifications of the soma, without any change of constitution of 

 the tissues, or of the nuclei. But others are oi the nature of shortn ata 



instance, a prothallus may arise from the Fern Plant without th<- intervention 

 of spores (apospory), as in certain forms of Athyrium or Polystichum (Fig. 401, 



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A, B). Or a Fern-Plant may spring directly from a prothallus without the 

 sexual process {apogamy), as in Ptcris erotica (Fig. 402, C). Such example- show 

 that the events of the life-cycle are not immutable. But they raise difficulties 

 of interpretation in terms of chromosomes. 



In the relatively simple case of Dryophris pseudo-mas, var. polydactylum, 

 a young sporophyte is produced as a direct outgrowth from the prothallus. By 

 a careful examination of the bud-forming tissue it has been found that the bud 



