128 



PRINCIPLES OF PLANT-TERATOLOGY. 



phenomenon has been observed in some other plants, 

 e.g. the lesser twayblade (Listera cordata) (PL IX, 

 figs. 1 and 2), Anthurium, Lycojpodium cemuum, and in 

 the ferns Dvplazium and Plat y cerium. 



For the numerous other cases of shoots arising 

 adventitiously on roots, the reader must be referred 

 to the literature on the subject. 



Fig. 34 shows a shoot arising endogenously from 

 the root-tuber of a dahlia. 



Fig. 34. — Dahlia. Adventitious shoot developing endogenously from a 

 root- tuber. (After Carriere.) 



STEM-S BOOTS. 



Describing those, in the first place, which arise 

 from the more external tissues, there are very few 

 cases where these arise from the leafy stem, unless 

 this has been injured or artificially mutilated. In the 

 club-moss (Lycopodium Selago) great numbers of 

 bulbils or buds are formed exogenously near the apex 

 of the stem in the same position as the leaves ; they 

 are clearly not in the leaf-axils ; they drop off and 

 thus reproduce the plant. This is a normal character 

 of the species and may have arisen as a "sport" in 

 the past. Again in L. aloifolium adventitious buds 

 qtow out at the base of the stem. In both these cases 

 the shoots must be regarded as occurring on the leaf- 

 bases, as the whole stem is probably clothed with 

 these^ The shoots of Begonia pJiyllomaniaca are often 

 covered with small buds. 



Adventitious shoots on stems are usually formed as 

 a result of mutilation. 



