GROWTH AND WORK OF PLANTS 



foliage leaves, while scale leaves are borne on the subterranean 

 stem. Grasses with subterranean stems (root-stocks) are in some 

 descriptive works said to be " stoloniferous." But this is not in 

 accordance with the strict use of the term stolon since it does not 

 apply to subterranean stems. The root-stocks of the bracken 

 fern and sensitive fern do not bear aerial branches, but the large 

 leaves which arise from the subterranean stem have stout, long, 

 leaf stalks which serve to lift them up into the air and light. 



70. Root-stock of Iris. The root-stocks of Iris are irregularly 

 club-shaped, with prominent concentric rings and stout, fleshy 



roots. Branching of the root- 

 stock takes place near the up- 

 per end. These branches arise 

 in the axils of old leaves and 

 first appear as conical buds. 

 In plants a few years old the 

 branching system is readily 

 seen. In the depressions the 

 concentric rings are the scars 

 formed by the falling away of 

 the leaves, the scars marking 

 the point where the leaf bases 

 were attached. In these leaf 

 scars are numerous minute pits, 

 the scars of the nbro-vascular 

 bundles of the leaf. 



71. Decumbent stems. These are stems which arise in an 

 ascending manner and then curve or droop to the ground, where 

 they often take root at the tip and form here a new decumbent 

 stem, so that the plant slowly travels and spreads over the ground. 

 The blackberries and raspberries are decumbent stems. The 

 " walking " fern travels in a similar way but it is the long narrow 

 leaf which is decumbent. The tip of the leaf strikes the ground 

 and organizes a stem which develops roots and new leaves. 



72. Crown stems, or acaulescent plants. The dandelion 

 is a good example of this kind of stem. These are sometimes 



Fig. 43- 

 Root-stock of iris. 



