364 PROCEEDINGS OF THE ACADEMY OF [Juue, 



is sufficient to allow for a fair development without subsequent 

 change. May we not borrow a simile frotn a class of metaphysicians 

 who contend that " man is not merely a creature of cii'cumstauces, 

 but his character is mainly made for him and not by him," and 

 believe that an inborn direction, and not environment to :iny great 

 extent, is the ruling power in vegetable life ? 



What is the nature of this power that is capable of bending 

 with ease and without a break an old branch or trunk of a thick- 

 ness thai would require an immense mechanical pressure for man 

 to accomplish ? How does it operate ? 



In the paper already cited' I drew attention to the fact that the 

 life-growth of a plant was in a measure a struggle against gravita- 

 tion, and that a great part of the nutrition prepared by the plant 

 was spent in supplying energy in this struggle. Consequently when 

 a plant received extraneous aid in the contest, the extra nutrition 

 saved by this assistance was diverted to extra growth and luxu- 

 riance. Many observations have since shown that to energy trans- 

 muted from nutrition we have to look for the various forms that 

 plants assume. To the highest degree of energy we may attribute 

 the chief triumph of growth force over gravitation. This is ex- 

 emplified in the leading shoot of Pine trees. Observers know that 

 in this leading shoot the highest vegetative force is exhibited. It 

 so successfully resists all gravitating influences that it is drawn in 

 no degree from an exact perpendicular. If, however, the main 

 growing shoot of a vigorous tree is broken off, the extra nutrition 

 diverted from the centre to the lateral branches supplies one of 

 these with an extra degree of energy, and a new leader arises in 

 place of the lost one. From this Ave deduce the law that plants 

 are engaged in a contest with gravitation, and that geotropism is 

 in proportion to the degree of energy lost in the contest. 



Going over the list of plants enumerated in this paper, we note 

 that decumbency is in proportion to the decline of vigor, and we 

 find this to be the case in individual trees generally. Whal are 

 known in gardens as fastigiate trees, of which the Lombardy 

 Poplar is a type, ai-e remarkable for the vigor of the central shoot 

 and laterals. Weeping trees, on the other hand, are characterized 

 by decreased vigor. The normal form of Salix Japonica, of 

 which the so-called Babylonian Willow is an offspring, is very 



^Proc. Acad. Nat. Sci. PInln., 1866, p. 401. 



