6o CHANGES OF COMPOSITION [chap. 



up a large reserve store of food to carry the plant in a 

 resting condition through periods of summer drought. 

 Perhaps the most instructive example is afforded by the 

 Autumn Crocus {Colchicum), which, as a wild plant, is 

 abundant in the west country pastures, and, with its 

 allies, is also not uncommon in gardens. The noticeable 

 feature about the autumn crocus is that it throws up 

 its blossoms without any leaves in the autumn, the 

 flowers being followed sometime later by the seed pod ; 

 in March the leaves appear and grow to a considerable 

 size without any sign of blossom. During the growth 

 of the leaves, a corm (the equivalent of the bulb 

 in this case) is formed, and grows to a considerable 

 size, being packed with starch, etc., which is manu- 

 factured by the leaf and transferred for storage to 

 the corm. Towards the end of June the leaves die 

 down entirely and the plant goes to rest, still, how- 

 ever, respiring slowly in the corm, such respiration being 

 a necessary condition of vitality. With the autumn, 

 however, the corm renews its vigour, the flower stems 

 are thrown up, but all the material therein, as well as 

 that required to support the rapid respiration which 

 attends the flowering period, is drawn from the material 

 that had previously been stored in the corm. As far as 

 the plant goes, this is a period of pure spending of its 

 accumulated resources, because the plant no longer 

 possesses any leaves or other green organs capable of 

 assimilation; the corm itself becomes depleted, but 

 under favourable conditions a quantity of seed is formed, 

 capable, by its food store, of reproducing the species 

 and giving it a start in the next generation. The corm 

 itself also retains enough food material to carry it 

 through the winter and start new leaves which will 

 build up the reserve afresh in the spring, thus repro- 

 ducing the same plant in the following year. With 



