THE VIOLET FAMILY 263 



honey, therefore, will encounter with its tongue the pollen 

 collected on the hairs of the petal, and, in drawing back its 

 head, will force the little platform on the style against the 

 stigmatic surface, and thus protect the flower from self- 

 pollination. In going to another flower, the insect will 

 naturally brush the upper side of the projecting lid, when 

 entering the flower, and thus cross-pollination will be effected. 



Cleistogamic Flowebs in the Genus Viola. 



Although cross-pollination is essential to the welfare of many 

 plants, there are many others in which self-pollination results 

 in the production of good seeds. In other cases, flowers which 

 are usually cross-pollinated, become adapted for receiving the 

 pollen from their own stigmas, when, from some reason or 

 other, cross-pollination fails. Under these circumstances 

 many plants produce what are known as cleistogamic flowers. 

 {Cleistogamic, from the Greek, meaning concealed marriage). 

 These are flowers which never open, but which nevertheless 

 produce seed, as a result of the application of their own 

 anthers to their own styles. Cleistogamy is known amongst 

 plants belonging to widely divergent orders. Thus it is found 

 amongst species belonging to the following genera : — Arabis, 

 Azalea, Gentiana, Hypericum, Oxalis, Veronica, etc. Probably, 

 however, it is better known in the genus Viola, than in any 

 other. 



Cleistogamy is generally resorted to, when wet weather 

 prevails about the time when the flowers should open, or when 

 the plants themselves happen to grow in moist or shady 

 places. This method of pollination is sometimes effected by 

 mechanisms as ingenious as those found in plants which are 

 cross-pollinated. The petals which are no longer required 

 for the attraction of insects, become rudimentary, or are 

 altogether wanting. When they are present, they are 

 generally greenish, or greenish-white. The anthers are so 

 situated, that they come into contact with the stigma as soon 



