194 



A TEXTBOOK OF BOTANY [Ch. IV, 11 



case the stem acquires more chlorophyll, shown by a deeper 



green color, thus 



supplementing better the work of the 

 leaves ; but in others the leaves 

 are reduced in size almost to dis- 

 appearance, leaving the foliage 

 function wholly to the slender- 

 cylindrical stems and petioles. 

 In others the stems hiecome 

 flattened, thin, and green Uke 

 the leaves, as in the familiar 

 greenhouse plant Muehlenheckia 

 fFig. 139), the stem nature of 

 which, despite its deep green 

 color, is proven by the prominent 



Fig. 1.'j'.i. — Muehlenbfckia plafy- 

 clarla ; y\. ^From Goebel.) 



nodes and the persistent 

 ^mall leave':, .^till more 

 striking are the cases in 



which flattened stems, in ''"'■ '*"■ ^ Leaf-like eladophylla 



,, ■ , , ' ibranfhes) of Butcher'.s-Broom, Ruscus 



this case branches, Ije- Hypoglo.,sv.m. in the axils of bracts, and 



come limited in growth, ^^aring leaves and flowers: X 5. (After 



, , " . . KeViicr.) 



anfl assume rliaracten~tic 



leaf shapes, to such a degree that theii- stem nature would 



hardly be suspected at all, were it not that they grow from 



