OF THE EMBRYO AND SEEDLING. 



21 



mained short and subterranean, and is confluent with the upper 

 part of the thickening root : the seeming caulicle, which raised 

 the cotyledons above the soil, consists 

 of the petioles of these combined into 

 a tubular stem-like bod}-, no evident 

 trace of which is visible in the seed, 

 although in germination it attains the 

 length of two or three inches : in age 

 it is readily separable into the two 

 leaf-stalks or petioles of which it is 

 composed : the plumule is thus seen 

 to be wholly normal, originating from 

 between the cotj'ledons. All the ex- 

 tensive growth so far, and until the 

 proper foliage-leaves of the continu- 

 ation of the plumule are developed 

 and begin their action, is from nutri- 

 tive material stored in the thickened 

 cotyledons, a considerable part of 

 which was transferred to the already 

 enlarging root, before a remaining 

 portion was used in building up the 

 strong plumule. The economy of this 

 elevation of cotyle- 

 dons which never 

 open, and of the 

 lengthened distance 

 through which the 

 nutritive matter has 

 to be carried, is not 

 apparent. But it is 

 the family habit in 

 Cucurbitaceae to 

 bring up the cotyle- 

 dons that they may 

 develop as leaves 

 (as in the Pumpkin, 

 Fig. 47) : here this 

 elevation is brought 

 about in a different way, but without securing the useful end. 1 



1 It may be inferred that Megarrhiza is a descendant of some Cucurbitacea 

 with thinner cotyledons, which in germination developed into long-stalked 

 leaves, in the manner described in the next following paragraphs. 



FIG. 43, 44. Peculiar germination of Megarrhiza Californica; explained above. 



