28 Flowers and their Unbidden Guests. 



and of the leaves ; and thus it is self-evident that any 

 very extensive injury of these parts would also inter- 

 fere with the perfect development of the blossom. 

 Stem, therefore, and leaf-formations must, for a certain 

 period and to a certain degree, be secured from the 

 destructive attacks of animals, if for no other reason, 

 yet in order that the material required for the forma- 

 tion of ilowers and fruit may be forthcoming. 



It will, therefore, I think, not be out of place to 

 devote a few pages to the methods by which leaves and 

 stems are protected. 



A. — -Protective Appliances of the Leaves, im, which an 

 formed the Materials for the Flowers. 



In very many species of plants the foliage is pre- 

 served from any extensive^ destruction by means of 

 Certain alkaloids and other chemical compounds con- 

 tained in the cellular juice. The leaves of Datura and 

 Solanum, of Aconitum, Helleborus, and Paeonia, of 



1 Minor injuries which interfere but slightly with the function 

 of the leaves cannot here be considered. The leaves of Atirop: 

 belladonna L., for instance, may be eaten through and through by 

 Haltica atropce All., and yet neither the development of tie 

 flowers nor the ripening of the fruit be in the least impeded. I do 

 not mean to say that smaller animals than those referred to in tbe 

 text may not do material damage to the foliage, or even destroy it 

 completely. Their attacks, however, are not unprovided against, 

 there being defensive appliances by which small creeping insects, 

 snails, etc., are kept off from the leaves. Thus, to give a single 

 example, the fimbriated cuflFs constituting so many " weels," which 

 are set round the petiole of Begonia mamcata Vis., make it impos- 

 sible for a snail to crawl up and get at the juicy blades. 



