190 SIGNIFICANCE OF MALFORMATIONS IN ORGANOGRAPHY 



extended over the whole plant. In the vegetative region abnormalities 

 were occasionally noticed, but all plants did not react in like manner. 



We may here merely direct attention to the long known fact, which 

 has been mentioned above, that in a number of plants, for instance Digitalis 

 purpurea, the formation of peloria is inherited through seed ; Peyritsch 

 has proved it in Leonurus Cardiaca. In Galeobdolon and Lamium how- 

 ever the inclination to the formation of peloria, which we must here 

 assume to be latent only, is expressed if special external conditions give 

 the stimulus. 



We have also to bear in mind the fact that we can produce fasciation 

 artificially by causing the ' sap ' to flow rapidly and with great intensity 

 into a lateral bud which otherwise would only obtain a small part of 

 it. This is why fasciation is specially common in stool-shoots and in 

 sucker-shoots. In annual plants also like Phaseolus multiflorus 1 , and 

 Vicia Faba, if one cuts off the chief axis above the cotyledons the 

 axillary shoots instead of developing normally are then frequently 

 fasciated. On this kind of shoot there appear also not infrequently 

 ' double leaves 2 .' This happens particularly in plants with decussating 

 leaf-pairs like species of Weigelia and Lonicera. The phyllotaxy changes, 

 and instead of dimerous whorls trimerous whorls appear. At the limit 

 where these different arrangements meet we often find transition-stages 

 from a more or less deeply bifid leaf to two separate leaves stand- 

 ing close to one another ; such leaves however also appear although 

 the phyllotaxy is unchanged. They evidently arise because under the 

 influence of the increased nutrition the shoot forms three instead of two 

 primordia of leaves, and of the three two lie close together ; if the plastic 

 material sufficient for the development of two leaves flows to these then 

 they remain separate and form two leaves, if this is not the case then one 

 bifid leaf is developed 3 . Such malformations are found on shoots which 

 develop after lopping of the chief axis, but I have also seen them on 

 uninjured individuals of Weigelia which were richly nourished. 



Luxuriant shoots often exhibit other marked variations in the form 

 of their leaves, apart altogether from mere size, and these, although one 

 cannot perhaps speak of them as malformations, may fitly find some 

 notice here. In Symphoricarpus racemosus the leaves are commonly 

 simple and entire, but they are pinnatifid on luxuriant ' renovation shoots.' 



1 Sachs was the first who proved this in this species. 



a See J. Klein, Uber Bildungsabweichungen an BIattern,in Pringsh. Jahrb. xxiv, 425; Celakowsky, 

 t)ber Doppelblatter bei Lonicera Periclymenum und deren Bedeutung, in Pringsh. Jahrb. xxvi, i 

 the literature is cited here. 



3 Many authors interpret this as a more or less deep splitting of a leaf-primordium. I do not 

 think this view is correct. I regard it as quite similar to what is easily observed in the Cacteae, 

 namely, that increased nutrition leads to an increase in the number of the orthostichies. It would 

 take me too far to give an explanation in detail here. 



