THE STEM. 25 



the principle of the hollow column, as in the culms of grasses. 

 Overground stems may serve as receptacles for reserve materials, 

 and in this case the internodes may either be of considerable 

 length, as in the trunks of trees, which during winter contain 

 large quantities of starch, &c, or they may be much shortened. 

 A familiar example of such a condensed stem is the cabbage, in 

 which plant, however, nutriment is stored not only in the short- 

 ened stem, but also in the bases of the leaf-stalks. 



Overground stems which are not erect may have a greater or 

 less tendency towards the horizontal position, or, on the other 

 hand, they may compensate their want of strength by climbing. 

 Tn the former case, the first approach to a horizontal position is 

 found in ascending stems which grow obliquely upwards. When 

 a stem commences by being erect or ascending, and then turns 

 down and runs along the ground, it is said to be recumbent. The 

 opposite of this is seen in decumbent stems, which first run along 

 the ground and then become ascending. Lastly, the horizontal 

 direction may be taken from the first, when the term procumbent 

 or prostrate is employed. Such a stem is creeping if it gives rise 

 to adventitious roots at its nodes. A few terms that are applied 

 to branches which serve for the multiplication of plants may here 

 receive mention. Suckers are ascending branches of subterranean 

 stems. The green shoots commonly growing up from near the 

 base of standard roses are of this nature, and so are the new 

 "canes" developed each year from raspberry bushes. Stolons 

 are prostrate or reclined branches which take root at the end, 

 where a new shoot then grows upwards, and a fresh plant is thus 

 formed. Slender elongated stolons are runners, as in strawberry, 

 while short thick ones are offsets, as in house-leek. Short suckers 

 are also called offsets. 



Climbing Stems. — In many climbing forms the main stem 

 itself winds round and round a support. Such twining stems 

 form either right-handed or left-handed spirals. In the former 

 case, which is the commoner, and of which scarlet runner and 

 convolvulus are examples, the coils ascend from left to right, as 

 in a corkscrew. The exact opposite is the case in the hop and 

 certain other stems, which form left-handed spirals. Another 

 large class may be called tendril-climbers, since they possess irri- 

 table clasping organs in the form of tendrils, which are thin, 

 elongated, stem-like structures, capable of turning round and 

 round a support. Tendrils may be either modified parts of the 

 stem, or flower-stalks, or parts of leaves. In the cucumber 

 and vegetable marrow the tendrils are branches, while in the 

 vine they take origin opposite the leaves (p. 27). The same thing 

 is true of the Virginian creeper, where, in addition, there may be 



