38 The Unity of the Organism 



Following a killing frost in southern California a few 

 years ago, thousands of lemon trees whose normal foliage 

 had been destroyed put forth great numbers of new shoots 

 on their trunks and largest branches. Such new shoots may 

 occur anywhere and everywhere on the trunk and branches, 

 and since they rarely arise, so long as there is no occasion 

 for them because of the activities of the normal foliage, the 

 term "adventitious"* is appropriately applied to them. So 

 lemon-tree germ-cells and lemon-tree plant agens, or speak- 

 ing in terms free from speculative sophistry, lemon-tree 

 seeds and lemon-tree buds, are dependent for their origin 

 upon lemon trees. In other words, the tree is as essential to 

 a causal explanation of the seed and the bud as the seed 

 and the bud are to a causal explanation of the tree. 



Reproduction by adventitious buds among the higher 

 plants is so important from the organismal standpoint that 

 we must consider it a little further. One additional fact 

 which the reader should appreciate is that the method is by 

 no means an exceptional and insignificant thing in plant 

 economy. It is a regular way many trees have of perpetu- 

 ating themselves. An illustration of this even more striking 

 than that of the lemon tree is furnished by the Coast Red- 

 wood of California (Sequoia sempertnrens). A stump of 

 this tree, even a stump that has passed through a severe 



* The question of adventitious or cambium buds from lemon trees 

 sen i is not to have received much attention from botanists. Judging from 

 the distribution of the new growths in such an epidemic, as it might 

 be called, of budding as that which takes place under conditions like 

 those here mentioned, there is scarcely a doubt that very many of the 

 new branches arise quite independently of previous bud germs; in other 

 words, from some source not germinal until it becomes so under the 

 special conditions. The only experimentation on bud production in the 

 lernon with which T arn acquainted has been carried on by Prof. II. S. 

 Reed of the Citrus Kxperiment Station of the University of California, 

 at Riverside. Doctor Reed has kindly shown me the results of his 

 work and permitted me to make use of them in this connection. So 

 far as these experiments go, it seems that while leafless pieces of 

 branches kept under suitable conditions readily put out undoubted cam- 

 bium buds, these produce roots only. 



