360 



PLANT LIFE. 



prox'ision for welcome guests must be enumerated the meth- 

 ods of excluding unwelcome guests, which on account of their 

 size and habits are unable to bring about the desired transfer 

 of the pollen, while at the same time they rob the plant of 

 nectar or pollen provided for more acceptable visitors. 



Fig. 403. — Flower of CohiBa scandens, halved ; showing tufts of hairs on the base of 

 the filaments, of which there are five ; these close the bottom of the corolla cup where 

 nectar is secreted against intruders. Three-fifths natural size. — After Kerner. 



(i) Various obslructions with- 

 in the flower may render ac- 

 cess to the nectar impossible 

 to the smaller and weaker in- 

 sects, while allowing others 

 to reach it. Such obstruc- 

 tions are formed by folds, 

 hairs, and other outgrowths 

 upon the flower leaves or the 

 essential organs (fig. 403). 

 (ii) OtixtiiicliiDis outside the 

 Jtinver ma\' exclude crawling 



Fi(;.4o4.-Flower of ,1 saxifrage (.S„.y//;v!.f.i insCCtS. Such are Stickv SUr- 



cciitTovei-sa), protected against invasion -^ 



by the numerous sticky glandular hairs on faces and hail'S (fig. 404), 



the rlower stalk, ovuiary, and calyx. Mag- v o ^ ^./' 



nilied several diam -Alter Kerner. mOatS about the StCm lomied 



by cup-shaped lea\'es holding water, or those formed l)v 

 water in which swamp plants grow, (iii) The ti?ne of bloom- 



