50 Flowers and their Unbidden, Gtiests. 



tageous, and therefore unbidden, visitors. These 

 structures are generally special epiblastemes of the 

 epidermis, namely glandular trichomes, which have 

 the function of coUeters, inasmuch as their cells secrete 

 a viscid substance which is discharged on the outer 

 surface. This discharge either occurs spontaneously 

 by diffusion, or, in many cases, is determined, in 

 increased amount, by stimulation from contact with 

 animals, freq^uently indeed by the rupture of the cell- 

 walls occasioned by such contact. But it often 

 happens that there are no special epiblastemes, and 

 that the viscid secretion is discharged by the ordinary 

 epidermal cells. The cuticle in such cases separates 

 itself from the secreting cells, and the secretion is 

 discharged into the spaces thus formed under the 

 cuticle, which it forces up into a kind of vesicle. The 

 viscid matter then flows out, either spontaneously or 

 through the bursting of the vesicles in consequence of 

 some exterior pressure. 



The viscid matter is a colloidal substance, some- 

 times resinous, sometimes mucilaginous, or frequently 

 resembling the compound known as blastocoL It is 

 always tenacious, and adheres very readily to other 

 bodies. That mUky juice also may become viscid, when 

 discharged from the tissue and exposed to the air, I 

 shall have an opportunity of showing in greater detail 

 at the close of this chapter. 



The viscid substance is found most frequently on 



