230 CHARLES R. STOCKARD 



the roots, through the assimilation of which, cell multiplication 

 was made possible. In the birds and in the experiments with 

 fish eggs, the initial development is interrupted by a sudden 

 lowering of temperature and through this the chemical processes 

 necessary for cell multiplication are slowed or stopped and devel- 

 opment ceases. Although the stuff is available, the conditions 

 prevent its use. 



The case of the mammal is more closely analagous to that of 

 the plant. Here the fertilized ovum within the Fallopian tube 

 begins to develop and continues until it exhausts its initial supply 

 of oxygen, though there may possibly be here also an exhaustion 

 of nutriment as in the plan. Following this, the development of 

 the embryo is either stopped for a considerable time, as in the 

 extreme cases of the deer and armadillo, or it is temporarily inter- 

 rupted or slowed until the membranes have become established 

 or embedded in the uterus of the mother and a further source of 

 oxygen and nutriment is thus acquired. The placentation of the 

 mammalian ovum and the rooting of the plant in the earth as a 

 mother, are comparable processes. Any lack of perfection in 

 the process is either fatal or lowers the supply of necessary stuffs 

 and thus causes an abnormally slow rate of development and 

 growth with a resultant imperfection in structural formation. 



After the original linear sprout of the plant has rooted, and a 

 certain extent of linear growth has taken place from the apical 

 bud, growth in length gradually slows as if the apical bud had 

 passed bej^ond the point at which it could dominate the growth 

 activities throughout the length of the plant. When this time is 

 reached, the axillary buds at the base of the leaves are able to 

 express their growth capacities and the plant develops its lateral 

 branches. Though all the branches of a plant have a more or 

 less similar function, yet each may be looked upon as an organ, 

 and their origin and subsequent competitive growths are in many 

 respects similar to the origin and growth of organs in the verte- 

 brate embryo. 



Such a statement of the situation in plant development is 

 rendered further justifiable by a very common experiment. If, 

 instead of allowing the apical bud to gradually exhaust its suprem- 



