44 BOTANY 



to its stationary position, and the difficulties and 

 dangers which the latter presents, must be considered. 

 The adaptations which it shows and the changes of 

 climate which it meets are of great importance. 

 Finally, we have the relation of the shoot system to the 

 processes of reproduction. 



When the young shoot has emerged from the seed and 

 made its way into the air in the ways already described, 

 the bent or hooked form gradually changes till an up- 

 right position is attained. We have already examined 

 the behaviour of the young root, noting its perception of 

 direction and its modification of its growth if necessary, 

 till it can make its way vertically downwards. The 

 same appreciation of direction is exhibited by the young 

 shoot and its behaviour is very similar, with the im- 

 portant difference, however, that it seeks the light and 

 air and hence grows vertically upwards. We cannot 

 explain this difference except by recognising the pur- 

 poseful character of its response to the influence of 

 gravity. There is no difference in the growing cells, so- 

 far as we can see, for they have all practically the same 

 structure whether they are in root or shoot. We see in 

 this behaviour really a living organism trying in a. 

 limited way to make the best of the circumstances in 

 which it finds itself. As we continue to study it we 

 shall be able to ascertain that it possesses the same 

 sensitivities and powers of response to changes in its 

 surroundings that we have found exhibited by the root. 



The growth of the shoot, however, is a much more 

 complicated process than that of the root, in conse- 

 quence of its more manifold duties, which have called 

 for a more complicated structure. 



The young plumule when it has emerged from the 

 seed coats consists of a very delicate axis, at the apex 

 of which a number of minute outgrowths are to be seen. 

 These are folded in various ways, the outermost covering 



