87 



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k 



ceptlon which has so long been the prevailing notion In regard to 

 plant metamorphosis. In one of these experiments the effort 

 was made to prove that the sporophyllum (fruit leaf or 'fertile 

 leaf) o{ Boirychmm Licnaria was the result of the transformation 

 of a foliage leaf* FaiHng to prove this experimentally, the 

 attempt was afterward repeated with Oiioclea struthiopteris and 

 satisfactory results obtained. 



He explains what may be considered experimental proof as 

 follows : It is necessary to show that the beginnings of the sporo- 

 phyllum and foliage leaf agree, and that it is possible to cause 

 such foundations, as by undisturbed growth would have de- 

 veloped into fertile leaves, to develop into foliage leaves. It is 

 also especially desirable to cause transition forms between foliage 

 and fertile leaves to appear. This is the case because the begin- 

 nings of both kinds of leaves, until a relatively late period of 

 development, are so similar that it is only by transition forms 

 that it is possible to determine with certainty whether the organ 

 in question is really a fertile leaf changing to the form of a foliage 

 leaf, or only a common foliage leaf 



Among those ferns which show a difference between fertile 

 and foliage leaves, the genus Onoclea is the most striking. The 

 examples chosen for the experiment were large, healthy, well- 

 developed plants- At different times all the foliage leaves were 

 removed, thus causing an abnormally rapid growth of those un- 

 developed foundations of both foliage and fertile leaves which 

 were already formed. 



. Naturally, only those plants in which the fertile leaves were 

 already started and whose sterile leaves were unfolded, were of 

 use in the experiment For example, one whose leaves were 

 removed the loth of May, before all the foliage leaves had 

 unfolded and probably before any fertile leaves had started, in 

 the course of the summer produced eleven sterile and one per- 

 fectly normal fertile leaf In the other examples the leaves were 

 removed later in the season, after the foHage leaves had unfolded 

 and the beginnings of the fertile ones formed. In these cases the 



*Vergleichende Entwicklungsgeschichte der Pflanzenorgane : Schenks Handbuch 



ni., page III. 



