140 Introduction to Botany. 



having a function quite different from that of typical 

 stems, their morphological nature is made clear by their 

 much reduced scale leaves, in the axils of which buds occur 

 (see Fig. 68). Such modified stems also have a reproduc- 

 tive function, since, after they have survived the winter, 

 their buds develop into new shoots. Stems which are 

 modified for the purpose of multiplication are illustrated 

 by the above-ground runners of the strawberry and the 

 underground runners of the goldenrod. The yellow water 

 lily, Nelumbo bttea, affords an example of a stem which is 

 at first slender, and runs along in the mud beneath the 

 water for the purpose of multiplication, and later becomes 

 much enlarged in certain of its internodes for the purpose 

 of storage (see Fig. 69). 



The leaflike structures of Ruscus are really stems, as is 

 shown by the fact that they do not bear buds in their axils, 

 but are themselves borne in the axils of scales which have 

 a regular angle of divergence on the main stem ; the 

 scales being, therefore, morphologically, leaves, and the 

 leaflike structures, stems. But we have still further evi- 

 dence, for the leaflike structures, termed cladophylls, bear 

 flowers in the axils of scales that are evidently leaves (see 

 Fig. 70). To sum up the evidence : The cladophyll is 

 borne in the axil of a leaf, and itself bears a leaf and 

 flowers. The evidence is, therefore, strong that it is a 

 stem. The fact that it looks like a leaf and performs the 

 photosynthetical function of a leaf should not be taken as 

 evidence that it is not a stem, for we have already seen 

 that the forms of plant members can vary indefinitely, and 

 that they may be put to a variety of uses. The green, 

 thick stems of cacti perform the double function of storage 

 and photosynthesis, while the leaves have become reduced 

 to spines that have entirely lost their normal function of 

 photosynthesis. 



