124 ELEMENTARY BOTANY. 



of the stem begins to turn yellow ; later, lignification sets in, 

 to the detriment of the fibre. The unripe seeds may be used 

 for oil, but not for planting. The plants are pulled out of the 

 ground and subjected to a process of retting, either by dew, 

 cold or warm water, or steam, by means of which the bast is 

 loosened from the stem, and more or less decomposed into 

 fibres. The best flax is very lustrous. That which is lustre- 

 less is contaminated with cortical parenchyma. The bast cells 

 of which it is composed have the walls so thick that the cavity 

 is nearly closed. 



10. The very important textile fibre. Hemp, consists of the 

 bast of Cannabis saliva, a dioecious species of the Nettle family 

 ( Urticacex), growing six to ten feet high, having long pedate 

 leaves, with five narrow leaflets, and inconspicuous flowers. 

 It is supposed to be a native of the warm parts of Asia, and 

 is found in cultivation in Africa, North America, Australia, 

 and elsewhere. It has been used in Europe several hundred 

 years. It must be harvested for the flbre before the maturity 

 of the seed; the latter can then be used in obtaining oil. 

 The pistillate plants when grown for the seed must be al- 

 lowed to ripen. The process of retting is similar to that em- 

 ployed in the case of flax. The color is often white, but the 

 gray is the best. It is lustrous. The cavity of the cell is about 

 one-third of its diameter. The Hemp plant is used as an intox- 

 icant for chewing and smoking by over three hundred millions 

 of people. Its narcotic effect is due to a gum-resin existing 

 in the leaves and flowers ; it is called " hasheesh." The seeds 

 of Hemp contain thirty-four per cent, of oil, most of which 

 may be extracted by pressure. It is a drying oil, greenish at 

 first, then becoming j'ellow, and is used in mixing paints, 

 making soap, etc. China Grass, Bcehmeria nivea and B. tena- 

 cissima, perennial herbs, belonging to the Nettle family ( Urti- 

 cacese), have been cultivated in India since very early times, 

 for their excellent fibre called Ramie. It cannot be readily 

 separated from the epidermis and surrounding tissue. The 

 bast-cells have a very large diameter. They are dirty green, 

 whitish, yellowish or light brown, and are very tough and 



