LIFE HISTORIES OF FAMILIAR PLANTS 



one large tuber, and possibly the decayed and 

 shrunken remains of another ; and again, as winter 

 approaches, we should find a similar contrast. The 

 large tuber left before winter, is that which is to 

 supply the material for the growth of the following 

 spring and summer. Later the leaves assimilate 

 further material, and from this a new tuber is 

 formed as a storehouse for the next season's 

 growth ; midway in the season we find a pair or 

 tubers of almost equal size, but they differ in that 

 while one is half exhausted the other is but halt 

 formed. 



This arrangement of two tubers, one for present 

 and the other for future use, is peculiar to the 

 orchids, and the significance of this device has not 

 to my knowledge been observed. Now my ex- 

 amination of the roots of a number of these plants 

 to-day suggests that the spotted orchis has adopted 

 by this double organisation of its root-functions a 

 most practical and most ingenious device. Look 

 again at Fig. S2 (Plate 57), and note that each 

 tuber takes opposite directions. Glance at the 

 example on the lefi: of the photograph, and observe 

 the pale-coloured conical bud that appears at the 

 apex of the tuber against the stem. From that 

 bud will come the main stem of next season's 

 growth. 



Now it is obvious that, if the newly-formed 

 tuber directs its course in the opposite direc- 

 tion to the old one, when the latter perishes, 

 together with the stem, the new tuber is left alone 

 on new ground. Then, in due course, when 



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