VEGETATIVE AND SEXUAL REPRODUCTION 171 



ovary at its point of junction with the latter. The stigma termi- 

 nates the style and is surrounded at its margin by a circlet of hairs 

 which point obliquely upward. Below the stigma is a hairless 

 space, about one 

 fourth of a milli- 

 meter in length, 

 which separates 

 the bristles encir- 

 cling the stigma 

 from the stylar 

 brush. This sty- 

 lar brush is com- 

 posed of a zone of 

 hairs on the style 

 from one to two 

 millimeters long. 

 The bristles ar- 

 ranged in a circle 

 around the stigma 

 are often called 

 protective bristles, 

 since they are 

 supposed to keep 

 the pollen of the 

 stamens away 

 from the stigma 

 of the same flower. 

 The hairs of the 

 stylar brush are 

 termed collecting 

 hairs, since they 



collect and hold the pollen which is discharged upon them by 

 the early opening of the adjacent anthers. The stigma, which 

 is protected from its own pollen by the protective circlet of 

 hairs, is sticky and remains receptive to foreign pollen long after 

 the pollen from the anthers in the same flower has been shed 

 and removed. The wings and the keel are yoked together and 



FIG. 90. Black locust (Bobinia pseudo-acacia) 



a, winter twig; b, section through a lateral bud; c, com- 

 pound leaf; d, inflorescence; e, flower enlarged, with 

 stamens and pistil exposed by removal of part of the corolla ; 

 /, fruit, or legume. After Otis, from " Michigan Trees " 



