Photo 6y] IE. Step. 



FIG. 439. SWEET VIOLET (Viola odorata). 

 Showing the reversal of the flower by the curving of the flower-stalk. The plant to the left is the white-flowered form. 



CHAPTER XII 



THE WELCOME OF THE FLOWERS 



'Jhese have their sexes! and when summer shines. 

 The bee transports the fertilizing meal 

 From flower to flower, and e'en the breathing air 

 Wafts the rich frize to its appointed use. 



COW PER. 



rriHE important part which insects and other external agents play in 

 -L the fertilization of flowers was indirectly alluded to in the last 

 chapter, and we propose now to follow out this interesting subject in 

 some detail. 



The insects which visit flowers may, for popular purposes, be divided 

 into two classes bidden and unbidden guests ; the former being useful to 

 the plant, the latter useless. It may be added that an insect which is a 

 welcome visitor to one kind of flower may be an unwelcome visitor to 

 another ; so that the terms " bidden" and " unbidden" have only a relative 

 significance. Incidental allusion has been already made to some of the 

 contrivances in plants for the exclusion of certain visitors ; we may now 

 consider a few more of these contrivances, with special reference to the 

 flower. 



Of the necessity of excluding various kinds of insects from certain 

 flowers there can be no question. " G-uests might come," says Dr. Ogle, 



358 



