STRUCTURE AISD DEVELOPMENTAL RATE 241 



lar moment desired and it later continues until further critical 

 stages are interfered with. In this way, as a rule, we obtain 

 specimens with several regions or organs deformed and rarely 

 secure a specimen simply defective in respect to the state of a 

 single organ or part. 



In plants the conditions are far more simple, and it is possible 

 to suppress or bring out a given bud at will. In spite of the fact 

 that we may not understand exactly how it is accomplished, it is 

 definitely the growth of one bud in a plant that prevents the 

 growth of another particular one. Similarly in the embryo prob- 

 ably the growth of a given organ holds back the initial growth 

 of another organ until the first organ has exhausted its power of 

 suppression. 



The two components of a double individual interact on one 

 another in a way which would strongly support the foregoing 

 interpretations. When the components arise in positions of equal 

 advantage on the germ ring their interaction is balanced and both 

 develop normally and are equal in size. When one component 

 possesses an advantage over the other, its growth tends constantly 

 to suppress the growth and development of its fellow, and the 

 inferior component is, therefore, deformed and arrested in its 

 development. 



When a growing shoot of a plant, such as the common privet, 

 has finally exhausted itself, the terminal bud goes into a dormant 

 or resting stage and stands only a little above the axillary buds 

 of the two uppermost leaves. After a certain interval of rest 

 the sh6ot may again begin to grow, and then one of several possi- 

 bilities may occur. In the first place, the terminal bud generally 

 possesses an advantage or occupies a more advantageous growth 

 position. It again shoots up continuing the line of the original 

 shoot. Its advantage is so complete that the uppermost axillary 

 buds are unable to express their growth potential and remain dor- 

 mant (fig. 1, plate 5). In the second place, the terminal bud may 

 again shoot up, but its growth is not so pronounced and it fails 

 to completely suppress the two uppermost axillary buds. One 

 of these being in some way more favorably located than the 

 other, also begins to grow a shoot in a direction at an angle to 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 28, NO. 2 



