ERECT FOLIAGE STEMS. 715 



The stalk (caidis) does not become woody, but remains green; it persists only for 

 a single period of vegetation, and then dies dow n. The stem of annual and bien- 

 nial plants classed as herbs (Iterhcv) is called a " herbaceous " stem (caulis herbaceus), 

 and tiuit of perennial plants a " suliruticose " stem {caulis suffruticosus). By the 

 term " underehrub " (sioffrutex) we understand especially those perennial plants 

 whose undergi-ound stem annually sends up shoots which do not become woody, 

 but which die oft' at the beginning of the winter, e.g. the Dwarf Elder (Sambiicus 

 ebulii^), tiie connnon Avens {Geum urbanum), and the Meadow ISage {Salvia pra- 

 teiisis). Whilst the caudex and culm are generally circular in cross-section, the 

 caulis is usually 3-, 4-, and 5-ribbed. Longitudinal furrows traverse its exterior, and 

 the relation of these to the neai'cst leaves will bo described more in detail subse- 

 quently. The extreme limits of size of the caulis have already been discussed on p. 656. 



The woody stem (truncits) either remains without branches until it has attained 

 a considerable height, when it is called " arborescent " {truncus arborescens), or it 

 is very short, and its branches spring from near the ground, in which case it is 

 called "shrubby" {truncus frutescens). A di.stinction is also drawn in descriptive 

 botany with regard to size between the " tree " {arbor) in the narrower sense, and 

 the " small tree " {arbuscula), the " shrub " {frutex) and the " small shrub " {fruti- 

 cxdus). The expression " semi-slirub " {semifi^tex) may be employed to denote 

 shrubs whose yearly shoots only become woody at the base before the next pei-iod 

 of vegetation, and which wither and die off above this. These form a transition to 

 the undershrubs mentioned above. 



Of all these forms of woody stem the tree, especially prominent on account of 

 its mass, naturally claims most interest. Nor is this interest limited to the botanist; 

 it is shared with him by the landscape-painter, forester, gardener, indeed, by every 

 lover of nature, each from his own pai'ticular point of view. Among all the forms 

 of vegetation trees are the best known; they have received a special name in all 

 languages, different nations have chosen certain species of their country as favourites, 

 and have extolled them as national trees in their songs, and even in the religious 

 observances and customs of ancient and modern times trees played and yet play a 

 prominent part. Many persons who have never occupied themselves with botany, 

 and have never observed plants closely, but who have a strongly-developed sense of 

 form, are able to distinguish and recognize the various kinds of trees at the first 

 glance and at considerable distances. How is this possible? The explanation is 

 very simple. The aspect of every tree, like the face of every man, presents certain 

 features which are peculiar to it alone; these features imprint themselves almost 

 unconsciously on the memory of anyone who is occupied much in the open, and the 

 species is recognized again by him, even at a distance, like an old friend one meets 

 in the street. To the landscape-painter these features, wliich, taken together, form 

 what has been termed the habit of the tree, are particularly important, for he has 

 to seize them and give them artistic expression. Our task here, however, is to 

 detail and to interpret these features in the appearance of the trees, or let us put it, 

 to give a scientific basis to the " habit ". 



