TERATOLOGY IN MODERN BOTANY. 



MALFORMATIONS have long- played an important 

 part in botanical literature. On the one hand, 

 every variation from that which we recognise as the 

 regular form (which, on that account, is naturally regarded 

 as the normal one) excites our interest, and on the other 

 hand, we are enabled to obtain, by the study of these mal- 

 formations, a deeper insight into the homologies of the 

 organs, and especially those of reproduction of the higher 

 plants. As I have dealt with this point elsewhere^ I will 

 not enter further into it here. For this period of Teratology 

 belongs essentially to the past. The present has turned 

 its interests to other questions. We ask rather now, what 

 gives rise to these malformations, and what is their bearing 

 upon the great problems of the origin of the organic 

 forms ? 



In endeavouring to indicate shortly the most important 

 contributions which have been made to the solution of 

 these questions, I must lay stress upon the fact that it is 

 not possible to define exactly what constitutes a malforma- 

 tion. No line of demarcation can be drawn between mal- 

 formation and variation, though one would be inclined to 

 lay it down as does Darwin," that " by a malformation is 

 understood any important modification of the structure of 

 such a kind as to be disadvantageous or even useless to the 

 species ". 



I. 



How do malformations arise } 



In attempting to answer this question, we encounter a 

 serious difficulty at the very outset. Whilst we see that 

 on the one hand they may be caused by definite external 

 lesions, on the other there is a mass of evidence to show 



^ See " Entwickelungsges. d. Pflanzenorg., Schenk's Handbuch, iii., i. 

 ^ Entstehung der Arten, p. 63, German translation. 



