DEVELOPMENT OF PLANTS 435 



marginal flowers have been lifted up by their filaments so that 

 they reach out and come in contact with the stigmas of the ad- 

 jacent inner flowers, the curvature of the styles often assisting in 

 bringing the two organs together. In this way, ample oppor- 

 tunity for crossing with the older flowers of another umbel is 

 first given and later a crossing between the adjacent flowers of 

 the same umbel is almost sure to result. In other cases, as the 

 snakeroot (Sanicula) a few of the simple flowers are perfect 

 while the remaining flowers of the umbel bear only stamens. 

 The perfect flowers are the first to open, being in the same con- 

 dition as the marginal flowers of the preceding example. Later 

 the filaments straighten out, curve away from the stigmas and 

 the anthers discharge their spores and finally drop off. Now the 

 adjoining flowers open and extend their filaments so that the 

 anthers are pushed over to the stigmas of the perfect flowers. In 

 the chervil, a similar crossing is effected after the perfect flowers 

 have shed their anthers by the numerous imperfect flowers grow- 

 ing above them and extending their anthers so that the micro- 

 spores will drop straight down upon the stigmas (Fig. 325). 



FIG. 325. Flowers of chervil: A, perfect flowers only in bloom. The 

 anthers are discharging their spores before the stigmas are receptive. B, 

 later stage the staminate flowers are now in bloom and shedding their 

 spores upon the mature stigmas of the perfect flowers. After Kerner. 



In the water parsnip (Sium), and beaked parsley (Anthriscus), 

 etc., there are two kinds of umbels, one containing principally 

 perfect flowers and the other only staminate flowers. The per- 

 fect flowers blossom first and shed their spores and anthers be- 

 fore the stigmas are receptive. After all the anthers have been 

 shed, the stigmas mature and continue in this condition for two 





