GLIMPSES INTO PLANT STRUCTURE 53 



knows, have a pithy stem ; and Eig. 34 shows a 

 magnified section of a rush stem. The centre of 

 the stem is not, however, hollow as it appears, 

 but is filled with very unsubstantial star-shaped 

 cells, which are too delicate for reproduction in 

 section. 



Fig- 35 represents a stem section, which seems 

 curiously irregular in form ; but when I explain 

 that it is taken from the stem of the common 

 ivy — which, the reader will remember, has tiny 

 tentacles or rootlets along its stem, by means of 

 which it adheres to walls and trees— the sha[)e 

 will readily explain itself. 



As a concluding example of stem structure, 

 Eig. 36 illustrates the central portion only of the 

 stem of a liana, or tropical climbing plant, which, 

 in some of the Brazilian forests, forms vast festoons, 

 passing from one tree to another, and so binding 

 tocrether all kinds of vey;etation in a maze of livino- 

 network. This stem will be seen to be light in 

 structure, probably owing to the plant's exceed- 

 ingly rapid growth in the humid atmosphere of 

 tropical forests, thus reproducing in an exaggerated 

 form the peculiarity of the tissue formed in English 

 trees in spring, when growth is quicker than at 

 other seasons. 



Rightly viewed, however, the stems of plants 

 are merely enlarged and permanent developments 



