PRIMULA CONFERENCE. 



251 



The development of the tufted stem from the plumule is well exemplified 

 in the case of the Cowslip, as pointed out to me some years since by 

 Mr. Holland. The seedling plant germinates in the usual way, but after a 

 time the weight of the rapidly-growing plumule causes the caulicle to bend 

 downwards and become more or less horizontal. Adventitious roots are then 

 thrown out from the base of the plumule, the caulicle and primary root 

 gradually decay, and thus the young plant becomes independent. (Henfrey's 

 " Elementary Course of Botany," Ed. 4, p. 654.) 



PROTECTION. 



One other provision with reference to the rootstock may here be noted, 

 and that is the manner in which in most species, notably in P. latifolia 

 P. graveolens, P. Palinuri, the deeply descending rhizome is protected from 

 loss of heat, as also from mechanical injury, by the dense covering afforded by 

 the remains of the old leaves. Contrast this state of things with the way in 

 which Auriculas thrust themselves out of the ground, their rootstocks showing 

 little or no trace of the leaves beyond the scar, which indicates the place 

 whence they have fallen. It would be interesting to ascertain whether these 

 peculiarities in the Auricula may not be connected with the development of 

 offsets (buds) from the side of the rhizome (fig. 24). 



Fig. 24.— auricula. 



Vertical rhizome ; the scars indicate the places whence the leaves have fallen. 



