100 SCIENCE PROGRESS. 



other whorls in the flowers into petals, and with these dis- 

 turbances there are connected numerous and far-reaching 

 ones in the structure of the composition of the flower as a 

 whole. 



Beyerinck ^ has been led to similar conclusions to 

 those of Sachs upon the question of the formation of galls. 

 He assumes that the substance secreted by the animal 

 possesses the character of an enzyme, and that there are 

 "enzymes of growth," which so effect the protoplasm of 

 host that gall-formation results. Beyerinck assumes similar 

 enzymes of growth in normal development of organs, only 

 that in this case they are produced by the protoplasm of 

 the plant itself. Since these enzymes must apparently be 

 difterent for each organ, his theory very nearly approaches 

 that of Sachs. 



We must, however, be satisfied with this short account 

 of the general question. And although the preceding ex- 

 position may be far from affording an exhaustive account of 

 the matter, it may yet suffice to show that whilst the object 

 and method of teratology in modern botany have changed, 

 the subject has not lost anything of its interest or importance, 

 rather the reverse. 



K. GOEBEL. 



