20 STEMS [CH. 



Male Fern, Dock, London-pride, Plantain, &c., for instance, 

 the stem is merely the short portion bearing the crowded 

 rosettes of leaves and scarcely projecting above the soil. 

 In sharp contrast to these are the tall stems of very many 

 common plants such as the Nettle, Sunflower, Willow, 

 Ash, Bamboo, Palm, Tree-fern, &c., and comparison shows 

 that the principal difference between these two sets of 

 stems depends on the elongation of those parts of the 

 axis situated between the leaves, and devoid of leaves : 

 the internodes, in other words, are very short in the first 

 case and long in the second, and many peculiarities of 

 stems are traceable to this difference in the degree of 

 elongation of the internodes as the shoot developes. 



Other differences are observed in the duration of the 

 stem. While that of a Banana, Palm, Pine, or Oak is 

 perennial, living for many years, those of many plants 

 are annual or biennial (Mustard, &c.). 



But it is evident that even the examples mentioned 

 differ in other points; thus the Banana, Palm, Tree-fern, 

 and many others do not usually branch, whereas most 

 ordinary shrubs and trees do so abundantly ; again, while 

 the Nettle, Daisy, and Sunflower steins are herbaceous, 

 those of the trees referred to are woody after the first 

 year. 



While it is useful and necessary to make these dis- 

 tinctions, however, the student should nevertheless under- 

 stand that the differences referred to are relative. This 

 is obvious as regards short and long internodes, but it is 

 also true of the duration of stems, for many plants, in one 

 country or under certain methods of treatment, throw 

 up annual stems, which under other conditions become 

 biennial, or even perennial. 



In the case of herbaceous, as contrasted with woody 

 stems, too, it must be understood that the soft stems of 



