208 ZSSSOJfS WITS PLANTS 



into a tube which encloses the single pistil, one 

 of them, A, remaining free along the upper side 

 of the tube. The stamens in the pea -like flowers 

 affect some such arrangement as this. 



238a. In some plants the stamens are united in a single 

 tube, and. are then said to be monadelphous ("one brotherhood"); 

 in other eases, as in the one before us, they are in two groups 

 or companies, or are diadelphous. 



239. If the parts of the calyx are five and the 

 stamens ten, we are surprised that the petals should 

 be only four, for we have found (172) that there 

 is a strong tendency for the envelopes and the 

 stamens to be represented by similar numbers or 

 by multiples of the lowest number. We are to 

 determine, then, if one of the parts of the corolla 

 represents the union of two petals. In certain 

 pea- like flowers the keel is represented by two 

 petals, whence we conclude that in the sweet pea, 

 garden pea, and other typical papilionaceous flow- 

 ers, the keel represents two parts. The corolla 

 of the pea, therefore, may be said to be built 

 upon the plan of flve. 



240. Plants which bear papilionaceous corollas, 

 ten monadelphous or diadelphous stamens and the 

 particular kind of pod (called a legume) which is 

 characteristic of the pea, are associated in a group 

 or family known as the pulse family, or Legumi- 

 nosse. (Pulse is the generic name of seeds of 

 peas, beans and the like.) 



