THE PRINCIPLE OF NUMBER. S3 



quinary ; but I am now more inclined to refer it primarily to 

 an inde6nite spiral series referable to the -/^ or ^\ type, 

 which has been reduced, perhaps through insect agency, by 

 symmetrical reduction to the present anomalous condition. 



The process of transition from a hypothetical indefinite 

 number of stamens to the present hexandrous state may be, 

 perhaps, seen by comparing the three genera of Gappai'idece 

 — Cajjparis, Polanisia and Cleome. The first has many 

 stamens and six placentas, which are sometimes reduced to 

 two. Polanisia has eight stamens, or more rarely six. Their 

 situations correspond exactly with those of the Cruciferce, 

 except tbat, when there are eight, there are four on the 

 anterior side instead of two. 



Lastly, Cleome brings us to the same structure as in the 

 Cruciferce with even the tetradynamous condition of the 

 stamens ; the elongated torus below the pistil being about 

 the only " capparidaceous " feature left. 



It is not at all uncommon to find more than six stamens 

 in cultivated plants of the Cruciferce, and when this is the 

 case T should be inclined to regard it as a tendency to a 

 reversion to a higher ancestral number. 



On the other hand, the close proximity of the two taller 

 ones on each side not infrequently brings about some degree 

 of cohesion between them, with an occasional arrest of half 

 an anther. This has led some to suppose that the pair have 

 resulted from chorisis. Since, however, their cords diverge 

 downwards to the right and left, and run down beside the 

 petalline cords (Fig. 6, b), this clearly proves that the union 

 is a result of close contact, and that the normal separation is 

 not due to chorisis, but to a primitive freedom, which has 

 been retained from a multistaminate condition. 



Pentamerous Whorls. — These are by far the commonest 

 amongst Dicotyledons. And as an enormously greater pro- 



D 



