BOTANICAL SUBJECTS. 283 



considering the glandular hairs of all other plants as homologous 

 with teeth. The teeth of other varieties of roses also, especially 

 those nearest the petiole, are often tipped with a gland, but in 

 these the teeth are not branched, as in the moss-rose. The teeth 

 of the sepals of the latter are no other than miniature branches 

 with secondary branched teeth on them, each limb or tooth, as I 

 said, having a gland at its tip. 



Not only the stem and midribs, but the nerves and veins of the 

 moss-rose have glandular hairs, so that the under surface of the 

 leaflets seems as if sprinkled with crimson pollen. 



There is abundance of evidence to show that prickles are only 

 modified glandular hairs,* for in those roses which have large and 

 small prickles on their stems, the small ones are all tipped with 

 glands ; otherwise they do not differ from the larger ones. As the 

 stem lengthens and thickens, the base of the prickle lengthens and 

 broadens. 



If we turn to the hop-plant we find that the stem is ridged. 

 On the ridges are minute hooked prickles. The ridges are not 

 unlike those of the horse-tail, which are also minutely toothed. 

 In the furrows between the ridges of the hop-plant are globular 

 hairs, which, in other words, are glandular hairs without the 

 stalk. The prickles are continued on the petioles, but on the 

 nerves they are changed into ordinary hairs. 



The base of the hop-prickle is small, and much resembles the 

 lenticels on the Elm and Elder stems,t so that perhaps it may be 

 permissible to consider that, after all, lenticels may be a further 

 atrophy of prickles, which existed in the ancestors of these trees, 

 in spite of the lenticels having a stoma on their summits. 



From all this it would appear that ordinary hairs, glandular 

 hairs, teeth and teeth prickles, and also stem prickles, and branches 

 are essentially one thing, and that they do not differ morpho- 

 logically from spines, which may be either abortive branches, 

 stipules, or petioles. Moreover, it would appear that the glands 



* J.G.Baker ("Journal Royal Horticultural Society," October 1889, 

 p. 208) says : " There is no hard and sharp line of demarcation between 

 acnlei, aciculi, and gland-tipped seta.'' 



t Compare with prickles on the supporting roots of the Palm, Socratea 

 exorrhiza (Royal Kew Grardens). 



