42, 43.] 



THE ESSENTIAL ORGANS. 



51 



membranous cell or sac containing a fluid. Its coat is 

 double the outer is more thick and firm, exhibiting 



Patten grains. Vfl, Pinus larico. 108, Basella rubra. 109, Ranunculus repens. 110, Scolymus grandi- 

 florus. Ill, Passiflora incarnata. 



one or more breaks where the inner coat, which is 

 very thin and expansible, is uncovered. In the fluid 

 are suspended mol- 

 ecules of inconceiv- 

 a b 1 e minuteness, 

 said to possess a 

 tremulous motion. 

 When the mem- 

 brane is exposed to 

 moisture, it swells 

 and bursts, d i s- 

 charging its con- 

 tents. 



1 Z L. in I 112 ^ gection of the Passion . flower (p ass iflora coerulea); 6, bracts 



rVirlcj a-nrl QilV-wroorl of the involucre ; s, sepals ; p, petals ; a, a, staminodia or sterile 



iiKweea filaments . c> stipe . 0> ovary . d Stamen8 . t> 8tigmas> 

 tribe, the pollen 



grains do not separate as into a dust or powder, but 

 all cohere into masses called POLLINIA, accompanied by 

 a viscid fluid. 



