40 



MARINE AND FISHERIES 



6-7 EDWARD VII., A. 1907 



sawdust some soluble material which was stored in the wood. This yellowish brown 

 solution was found to be exceedingly poisonous to fish eggs, fry, living organisms suit- 

 able for fish-food and adult fish. 



Pig. 1. 



SOURCE OF POISON. 



In order to understand the source of this poison we must try to get a clear idea of 

 the minute structure of trees. This can be done only by the aid of the microscope. 

 With this instrument, it is easy to see that all parts of young plants are made up of a 

 vast number of very small bladder-like compartments called cells. In older plants and 

 trees, these cells lengthen out and are then called vessels. It is important to note that 

 every cell or vessel consists of two principal parts, (a) the outside covering or cell wall, 

 snd (h) the inside matter or cell contents. If one were to imagine the cells in the comb 

 of a honey bee shrinking into such a small size that each one would be almost invisible, 

 then a very good idea would be obtained of the minute structure of a tree. The wax 

 would correspond to the walls of the cells composing a tree, and the inclosed honey 

 would correspond to the cell contents. 



In aquatic plants, like pond silk, the cells are cylindrical and placed end to end, so 

 as to form the long slender threads. In flat leaves, the cells are arranged side by side 

 in two or more layers, so as to form the flat surface ; in stems they are packed side by 

 side and end to end. Thus, trunk, branches, bark, roots, flowers and fruit are all made 

 up of these cells. In different plants they differ vastly in shape, size, thickness of walls 

 and contents. Bacteria are plants consisting of single cells; pines are composed of 

 millions of cells. In all plants also, the protoplasm, which is the central, living, moving, 

 sensitive part of the cell, manufactures different substances, and either packs these in 

 the cell as reserve material, which is the case in the higher plants, or throws them out 

 of the cell altogether as dead waste, which is the case in many of the bacteria. 



In order, therefore, to find out more definitely, if possible, the source of the poisons 

 given off by sawdust, we must look more closely at the contents of wood cells. 



CELL CONTENTS. 



Young cells are filled at first with protoplasm only. As time goes on, sap forms 

 in the cell and accumulates as small drops in the protoplasm. The sap consists of 

 water and nutritive material dissolved in the water. These two stages in cell life are 

 represented in Figures 2 and 3. Somewhat later, other substances which have been 

 formed by the activity of the protoplasm are stored in the cell, along with the proto- 

 plasm and cell sap. Among the commonest materials thus stored in cells are sugar, 

 starch, oils, such as olive, castor, linseed and palm oil; resins, gums. Jellies, alkaloids, 

 pigments, acids, such as malic, citric, tartaric and tannic, essential oils such as tur- 

 pentine. 



In the pine family there is stored in the wood and bark cells an abundance of 

 crude turpentine and resin. The Norway spruce of Europe furnishes, from cells, 

 turpentine and Burgundy pitch. The yellow pine of the southern United States yields 



