22 MOEPHOLOGY, OE COMPARATIVE ANATOMY. 



closely packed and more or less overlapping in the full-grown 

 plants. Such plants are sometimes, but erroneously, called acau- 

 lescent or stemless plants. 



The relative development of the internodes is next in importance to 

 the order of arrangement of the axillary huds in affecting the general 

 forms of stems. A clear idea of the conditions may be obtained by 

 examining, in the first instance, what occurs in the unfolding of the bud 

 of such a tree as the Horse-chestnut. In the bud the enveloping scales, 

 the rudimentary leaves, and even the blossom may be distinguished, 

 crowded on the undeveloped axis. As the leaves emerge and expand, 

 they become separated from each other by the elongation of the inter- 

 nodes of the stem, until at length they stand at considerable distances 

 along the sides of a shoot several feet long. This may be illustrated by 

 comparing- it to the separation of the joints of a telescope, when its 

 lengths of tubes are successively pulled out. Examples of permanently 

 undeveloped internodes are seen* in the rosette-like offshoots of House- 

 leeks and of many other herbaceous perennials in the first season's growth 

 of such plants as the Turnip, Carrot, Canterbury-bell, and indeed of 

 most biennials, where the leaves all appear to arise from the root in the 

 bulbs of many Monocotyledons, such as the Crocus, Hyacinth (fig. 17), 

 &c. In these cases the flowering axis which subsequently appears often 

 develops its internodes consider- 

 ably, and rises as a tall stem. An 

 intermediate conditionis metwith 

 in stems which are elongated, but 

 have the leaves closely overlap- 

 ping, as in the common Stone- 

 crop, many Coniferous trees, many 

 Palms (figr. 33), &c. ; and a simi- 

 lar condition exists in the sub- 

 terraneous root-stocks of various 

 plants, where the imperfect 

 sheathing leaf-scales succeed 

 each other at short intervals. 



Kegions of the Stem. In 



the embryo of a Flowering 

 plant it is scarcely possible to 

 define the limits even of the 

 stem itself, which loses itself 

 above in the plumule, and be- 

 low in the radicle. But in 

 fully-developed stems, a gen- 

 eral division into three regions 

 may be distinguished accord- A^^^, ^ with a creepl - ng rh; . 



ing to the kind OI lateral zome bearing leof-scales, an erect leafy stem, 



organs which they bear, viz: 



1. The Leaf -scale region (fig. 12), which is mostly subterranean 



