LEAF-LIKE STEMS 



55 



cactuses are cylindrical or prismatic, while still others consist 

 of flattened joints ; but all agree in offering much less area to 

 the sun and air than is exposed by an ordinary leafy plant. 



68. Leaf-like stems. The flattened stems of some kinds of 

 cactus, especially the common showy Phyllocactus, are suffi- 

 ciently like fleshy leaves, with their dark green color and imita- 

 tion of a midrib, to pass for leaves. There are, however, a good 

 many cases in which the stem takes on a more strikingly leaf- 

 like form. The common asparagus sends up in spring shoots 

 that bear large scales which are really reduced leaves. Later in 



FIG. 51. A spray of a common asparagus (not the edible species) 



the season, what seem like thread-like leaves cover the much- 

 branched mature plant, but these green threads are actually 

 minute branches, which perform the work of leaves (Fig. 51). 

 The familiar greenhouse climber, wrongly known as smilax, 

 properly called Myrsiphyllum, bears a profusion of what ap- 

 pear to be delicate green leaves (Fig. 52). Close study, how- 

 ever, shows that these are really short flattened branches, and 

 that each little branch springs from the axil of a true leaf, I, in 

 the form of a minute scale. Sometimes a flower and a leaf-like 

 branch spring from the axil of the same scale. 



