138 



PRINCIPLES OF PLANT-TERATOLOGY. 



axillary position, were obliged, owing to the absence 

 of the axis, to arise adventitiously on the outer scale- 

 leaves, through which they sent their roots. 



A very remarkable case of adventitious bud-forma- 

 tion on foliage-leaves recently came under the writer's 

 notice. Amongst the basal leaves of a plant of Ver- 

 bascum nigrum, affected with the " Crown Gall," from 

 whose " collar " sprouted a great mass of small shoots, 

 was one leaf whose margin was studded all round with 

 .adventitious buds giving the leaf an unusual appear- 

 ance. 



Beusekom gives a most detailed account of the 

 developmental formation of endogenous adventitious 

 buds near the tips of the leaves of Gnetum Qnemon. 

 They were induced both by the depredations of an 

 insect (Aspidiotus) and by minute needle- wounds. 



Ovary-Shoots. 



Adventitious buds also occur on floral organs, espe- 

 cially in the pistil. Peyritsch has described vegetative 

 buds sprouting from the placentas, e. g. in Sisymbrium 

 Alliaria, and apparently thereon replacing the ovules, 

 and the same phenomenon has also been observed 

 in the winter-cress (Barbarea vulgaris). Celakovsky 

 describes interesting cases in Sisymbrium Alliaria in 

 which the buds appeared in most cases on the virescent 

 inner integument of the ovule either on its upper 

 surface, when the integument was in the form of an 

 expanded leaflet or a pitcher, or on its lower face (on 

 outer surface of pitcher), in all cases at or near the 

 base of the organ (PI. XI, fig. 1). Penzig figures and 

 describes buds growing on the virescent ovule, but it 

 is not quite clear upon which integument they occur ; 

 they either grow out side by side with the elongated 

 nucellus, or from the tissue immediately underneath 

 the nucellus which then becomes raised up and borne 

 at the apex of the leafy bud. In all these cases of 

 adventitious buds occurring in the ovary, even where 



