IV.] TRIFOLIUM CARD AMINE GROUND-NUT. 85 



perfect flowers ; the others form a rigid pointed head 

 which at first is turned upwards, and as their ends are 

 close together, constitute a sort of spike. At first, I 

 say, the flower-heads point upwards like those of 

 other Clovers, but as soon as the florets are fertilised, 

 the flower- stalks bend over and grow downwards 

 forcing the flower-head into the ground, an operation 

 much facilitated by the peculiar construction and 

 arrangement of the imperfect florets. The florets are, 

 as Darwin has shown, no mere passive instruments. 

 So soon as the flower-head is in the ground they 

 begin, commencing from the outside, to bend them- 

 selves towards the peduncle, the result of which of 

 course is to drag the flower-head further and further 

 into the ground. In most Clovers each floret produces 

 a Httle pod. This would in the present species be 

 useless, or even injurious ; many young plants growing, 

 in one place would jostle and starve one another 

 Hence we see another obvious advantage in the fact 

 that only a few florets perfect their seeds. 



I have already alluded to our Cardamines, the pods 

 of which open elastically and throw their seeds some 

 distance. A Brazilian species, C. chenopodifolia, Fig. 

 35, p. 45, besides the usual long pods, Fig. 35, a a, 

 produces also short pointed ones. Fig. 35, b i5, which it 

 buries in the ground. 



Arachis hypogma is the ground-nut of the West 

 Indies. The flower is yellow and resembles that of a 

 pea, but has an elongated calyx, at the base of which, 

 close to the stem, is the ovary. After the flower has 

 faded, the young pod, which is oval, pointed, and very 

 minute, is carried forward by the growth of the 



