STEM 



5546 



STEPHEN 



the monocotyledons. The group in which the 

 cells are arranged in circular form around the 

 pith, as in our common trees, are the dicoty- 

 ledons. 



The stems of the latter plants consist of an 

 outer, protective covering of bark and a woody 

 layer containing the bundles of cells surround- 

 ing the pith. The cells are of several kinds. A 

 layer of cork cells lies just beneath the bark to 

 prevent loss of water; flexible, tough, fibrous 

 cells give strength to the stem; tubular cells 

 carry the plant food from the leaves; woody 

 cells form the channel through which the water 

 passes to the leaves from the root, and just out- 

 side of this woody section are the growing 

 cells, which form new bark on their outer side 

 and new wood on the inner side. The lifetime 

 of a tree is reckoned from the number of rings 

 or layers of new wood formed by these growing 

 cells. 



In some plants the stems live but a year, in 

 others two years and in still others, indefinitely. 

 The death of annual stems is not due to the 

 arrival of cold weather, as is often supposed, 

 but to the fact that the cells can develop only 

 a certain amount of new tissue, and when 

 growth stops, the stem dies. Thus the life of 

 the plant is limited to a certain period even in 

 regions where there is no cold winter and not 

 even a single frost. 



Stems vary greatly in thickness, ranging in 

 width from the immense trunks of the Big 

 Trees of California to the slender aspen stem 

 which is so delicate that the leaves constantly 

 quiver and softly rustle, giving the tree the 

 name "trembling-leaved poplar." The rate of 

 growth also varies in different plants. The sun- 

 flower and giant ragweed stalks grow ten or 

 twelve feet in a season, and slender, climbing 

 stems often grow forty feet in a single summer, 

 while many trees increase in height but one to 

 three inches a year. In the competition to se- 

 cure light and air, trees in dense forests and 

 plants in thick clumps grow tall and branchless 

 for a great height, but when growing alone they 

 are low and broad-topped. 



Underground Stems. The long, slender root- 

 stocks of the May apple, Solomon's seal, mints 

 and several other plants, the short, thick bulbs 

 of the hyacinth and lily and the familiar tuber 

 of the potato are underground stems. They 

 contain large quantities of stored food and 

 supply the plant when new food cannot be 

 made. Some produce an aerial stem and others 

 send up leaves and have no stem above the 

 ground, 



Reproduction by Stems. Many plants are 

 reproduced by portions of the stem. Our most 

 obnoxious weeds are those which have under- 

 ground stems, or rootstocks, which, though cut 

 by the hoe, produce a new plant at every node. 

 The slender, underground runners of the straw- 

 berry, the bulbs of the lily and tubers of the 

 potato also produce new plants. The black 

 raspberry forms a new bush by the rooting of 

 an ordinary branch, and many plants, such as 

 the snap willow, geranium, grapevine and cur- 

 rant bush are reproduced from cuttings, or 

 broken-off stems, which take root when planted. 

 The propagation of orchard trees by budding 

 and grafting is of vast importance in the mod- 

 ern cultivation of fruit. See GRAFTING. 



Economical Uses of Stems. The food ob- 

 tained from the stems of plants is of great im- 

 portance to man and animal. Cane sugar and 

 molasses and maple sugar and syrup are pro- 

 duced by the stems of the sugar cane and 

 maple tree; potatoes and onions are under- 

 ground stems; rhubarb, asparagus, celery and 

 other vegetables are aerial stems; syrup is de- 

 rived from cornstalks, which also are an impor- 

 tant food of horses and cattle. The fleshy 

 stems of the prickly pear cactus of the thorn- 

 less variety are another valuable cattle food, 

 and many wild animals, such as the deer, mo'ose 

 and rabbit, browse on the twigs and stems of 

 numerous plants. Common starch is derived 

 from the potato, and sago is made from the 

 starchy pith of the trunk of the palm tree. 

 Perhaps most, important of all has been the 

 employment of the wood of trees for building 

 purposes. W.F.R. 



STENCIL, sten'sil, a thin sheet of metal, 

 cardboard or leather with a pattern cut out by 

 means of interrupted lines or dots. It is used 

 in reproducing letters and designs. The stencil 

 is placed on the surface or material to be or- 

 namented, and a brush or sponge wet with ink 

 or paint is passed over it. Packing boxes are 

 often marked with stencils, and coats and 

 dresses are sometimes ornamented by stencil- 

 ing. The process is also employed in wall 

 decorations of a high class. 



STEPHEN, Steven (about 1097-1154), a king 

 of England, whose reign, lasting from 1135 to 

 1154, was one of the darkest in English history. 

 He was the third son of Stephen, Count of 

 Blois, and Adela, daughter of William the 

 Conqueror, and was a nephew of Henry I of 

 England.. In return for taking an oath to se- 

 cure the succession of Matilda, the king's 

 daughter, he was given large estates in Nor- 



