GLANDULAR HAIRS. 



[CHAP. 



common but beautiful Cornflower (Centaurea cyanus) 

 is quite smooth, but the involucres forming the 

 flower-head are bordered with recurved teeth. In 

 this case, neither the stem rior the leaves show a trace 

 of such prickles. 



The same consideration throws light on the large 

 number of plants which are more or less glutinous, a 

 condition generally produced, as, for instance, in the 



FIG. 31. Kntiutia dipsacifalia. 



flowers of the Gooseberry and of Linncza borealis 

 (Fig. 32), by the presence of glandular hairs. Kerner 

 has called attention to a very interesting illustration 

 afforded by Polygonum amphibium. In this species 

 the stigma projects about one-fifth of an inch above 

 the flower, so that if ants could obtain access, they 

 would steal the honey without fertilising the flower; 

 a flying insect, on the contrary, alighting on the 

 flower, could scarcely fail to touch the stigma. % 



