xv, 4 Oshima: Formosan Termites 339 



Besides the above-mentioned damage, that done to bridges, 

 telegraph poles, books, paper, wood pulp, cotton, and clothing 

 is sometimes very serious. 



PRINCIPAL FOOD OF COPTOTERMES FORMOSANUS 



The stem of an exogenous perennial is a complex of struc- 

 tural elements of varied form and function. Of these we may 

 distinguish three main groups: a, vessels; b, wood cells proper; 

 c, medullary tissue. The growing cell of plant tissue consists 

 of cell wall and protoplasm, the living functions depending upon 

 the activity of the latter. However, the above-named three 

 main structural elements of the wood do not contain nitrogenous 

 substance — that is, protoplasm — but mainly consist of the special 

 constituent of the cell wall known as cellulose. 



There are, as might be expected, a great many varieties of 

 cellulose, and the term must be taken as denoting a chemical 

 group. Cellulose, taken as a group, presents the following 

 characteristic : A colorless substance, insoluble in all simple 

 solvents; generally but variously resistant to oxidation and 

 hydrolysis • nonnitrogenous, having the empirical constitution 

 characteristic of the carbohydrates. The composition of pure 

 cellulose is represented by the percentage numbers C 44.2, H 6.3, 

 O 49.5, corresponding to the empirical formula (C fi H 10 5 ) x . It 

 is flexible, slightly elastic, permeable, but only slightly absorbent, 

 and does not readily undergo fermentation. When treated with 

 acid it passes into a starchlike condition, as is evidenced by 

 its turning blue with iodine; and under certain conditions in 

 the living plant it would seem capable of being formed from 

 sugar or of passing into it. 



It must be noted, however, that the typical cellulose is not 

 separated from the plant in a pure state, but in admixture or 

 in intimate chemical union with other compounds or groups 

 of compounds. The latter are distinguished by greater reac- 

 tivity; for example, they readily yield to alkaline hydrolysis, to 

 oxidation, or to the action of the halogens. In the latter is 

 included the very important group of lignified cellulose, or 

 lignocellulose, distinguished by the presence of ketohexene groups 

 in union with the cellulose, and therefore combining directly 

 with the halogens. 



Generally, walls of cellulose, fibers, and vessels in the wood 

 acquire mechanical strength or resistance by undergoing a 

 change known as lignification. This consists in their impreg- 

 nation with a substance known as licmin. forming a compound 



