BOTANICAL SUBJECTS. 2So 



Glandular hairs, whether stalked or stalkless, are to be found 

 on many plants belonging to different orders. And when we 

 consider that they are interchangeable with hairs and prickles, we 

 may consider them as a universal feature in pha^nogams. If not 

 found in one part they are found in another, so that they must 

 have some deeper morphological significance than that of mere 

 epidermal accidents. 



In the calceolaria we find that, on the outer or lower surface 

 of the sepals, the hairs are mostly ordinary hairs, while on the 

 inner or upper surface they are glandular. 



We see ordinary hairs on the petiole passing into glandular 

 hairs on the sepals in other plants. 



In the Dock., the hairs are half-way between ordinary and 

 glandular hairs. They are club-shaped. 



Various modifications of glandular hairs are met with. Some 

 of the hairs of the nettle become stinging hairs. These appear to 

 be only glandular hairs, with the apex prolonged into a fine tube. 

 On the turnip leaf are glandular hairs, like those of the 

 stinging nettle, only the glands at the base of the hair are 

 smaller. 



The reader may say these are very pretty speculations, but all 

 or most of the organs you have been writing about are epidermal 

 emergences. Quite so, but when needs be, vessels can be 

 projected into epidermal structures, as we see them in the 

 foliaceous emergences of the stem of the moss rose, and in the 

 tentacles of the Drosera. Moreover, in the sporangium of ferns, 

 and in seaweeds, important reproductive operations are carried on 

 without the aid of vessels. 



Dasya sarcocaulon has branches, which Harvey* calls 

 ramelli. They are nothing but branched hairs, made up of 

 simple strings of cells. vSo Jire the branches of many other 

 seaweeds. 



It would appear that as plants progressed in evolution, and 

 developed more complicated organs, suited to a more complicated 

 life, they did not always free themselves of the old homologous 

 organs, which may have become useless, but they often atrophied 

 them, and turned them to other, and perhaps, in the changed 

 circumstances, more useful purposes. Some of the ancient 

 persistent organs with altered function we now call hairs. In 



♦ " Pliyo. Aiistr.," pi. 278. 



