136 



While those that have to depend on external agencies are 

 usually less productive, and even though the progeny may 

 be found to have greater vegetative vigor, or some other 

 element of strength. 



Mr. Henslow says: "Thus orders of plants with easy 

 access to the honey are some of the most abundant, as 

 Hanunculaceae, Oompositae and Umbelliferae, as well 

 well as are those dependent upon the wind which never fails, 

 such as willows, Gyperacae, and grasses. On the other 

 hand all regularly self-fertilizing plants are abundant, and, 

 together with certain wind-fertilizing plants, are cosmo- 

 politan. " 



Cause for Gleistogamy- Kerner makes the follow- 

 ing suggestion in regard to the conditions affecting cleistog- 

 amous flowers: "No open, aerial flowers were produced 

 by Viola sepincola so long as it grew in the cool shade 

 of a dense wood, but when transferred to open ground, 

 accessible to sunlight, such flowers were developed. One 

 can hardly err in ascribing to the sun's rays a very import- 

 ant influence in stimulating plants to the inception of flower 

 ing shoots, especially such as bear blossoms possessing 

 bright-colored petals. Indirectly, however, this advantage 

 accrues to the plants in question, that, living as they do in 

 the deep shade, where no bees would, in any case, visit them 

 if they had open flowers, they can confine their constructive 

 energy to the inception and development of cliestogamous 

 flowers and save themselves the trouble of producing open 

 flowers adapted to cross-pollination (but useless in the place 

 in question). If the spot whei-e the violet grows becomes 

 exposed to the sunlight through the trees shading it being 

 blown down or felled, bumble and hive bees make their 

 appearance in search of honey, and buzzing from flower to 



