TYPES OF STEMS. 37 1 



721. The climbing type.— The grapes, clematis, some roses, 

 the ivies, trumpet crcejier, the climbing bittersweet, etc., are 

 climbing stems. I.ike tlic jjrostrate type, the climbers economize 

 in the material for stem Ijuilding. The}- climb over shrubs, 

 up the trunks of trees and often reach to a great height and 

 acquire the power of displaying a great amount of fohage by 

 sending branches out on the limbs of the trees, sometimes devel- 

 oping an amount of foliage sufficient to cover and nearly smother 

 the foliage of large trees; while the main stem of the vine may 

 be not over two inches in diameter and the trunk of the supporting 

 tree may be three feet in diameter. 



722. Floating stems. — These are necessarily found in aquatic 

 plants. The stems may l^e ascending or horizontal. The 

 stems are usually not very large, nor \-ery strong, since the water 

 bears them up. The plants mav grow in shallow water, or in 

 water 10-12 feet or more deep, Ijut the leaves are usually formed 

 at or near the surface of the water in order to Ijring them near 

 the light. Various species of Potamogeton, Myriophyllum, and 

 other plants common along th'e shores of lakes, in ponds, slug- 

 gish streams, etc., are e.xamples. Among the algas are exam- 

 ples like Chara, Nitella, etc., in fresh water; Sargassum, Macro- 

 cystis, etc., in the ocean. In these plants, however, the plant 

 body is a <^^hallus, which is di\'ided into stem-like {caulidiiim) and 

 leaf-like {pliyUidiiiin) structures. 



723. The burrowing- type, or rhizomes. — These are horizon- 

 tal, subterranean stems. The bracken fern, sensitive fern, the 

 mandrake (see fig. 4131/), Solomon's seal, Trillium, Dentaria, 

 and the like, are e.xamples. The subterranean habit affords 

 them protection from the cold, the wind, and from injury by 

 certain animals. Many of these stems act as reservoirs for the 

 storage of food material to be used in the rapid growth of the 

 short-lived aerial sh<wt. In the ferns mentioned, the subterra- 

 nean is the onlv .shoot, and this bears scale leaves which are 

 devoid of chloroph^-ll, and foliage leaves which arc larger, and 

 the onlv member of the plant l.iody which is aerial. The fohage 

 leaf has assumed the function of the aerial shoot. The latter is 



