INTRODUCTORY. 43 



CHAPTER XIII. 

 •Structure and Growth of Plants. 



A great amount of damage has occurred in some fruit grow- 

 ing districts of this State by the applications of solutions, etc., 

 as insecticides (i. e. a low grade of coal oil), which contained 

 properties that were detrimental to plant-life. By examining 

 Fig. 8, the outer bark is found to be represented by letter F, 

 the green layer by letter G, the inner bark by letter H, and the 

 camlHum layer by the letter I. As the cambium layer is" 

 stated in the following description to be the seat of life of the 

 plant, it may be readily understood in what maimer a solution 

 containing pernicious properties injures the tree when applied 

 to the outer bark, viz. : by penetrating the outer bark, the green 

 layer, and inner bark, thus reaching and destroying the cam- 

 bium layer (or sfeat of life of the tree). 



On the contrary, if proper solutions, such as are recom- 

 mended in this work, are applied, they destroy insect life, and 

 by penetrating the outer layers reach the cambium layer, and 

 by means of the fertilization properties which they contain, 

 invigorate the tree. 



[The following extracts are taken from a paper by Colonel 

 W. iS. Clark, President of the Massachusetts Agricultural Col- 

 lege. — Mass. Rep., 1873-4] : 



" Every seed and every young plant consists wholly of cel- 

 lular tissue, but with the development of leaves is combined 

 the growth of fibro-vascular tissue." 



" The first vessels to appear in the plantlet are arranged in 

 a circle around a column of tissue, which remains loose and 

 soft, and after the first season dries up and dies. This is called 

 the pith, and seems essential to the life of every woody stem 

 and branch during its infancy, although its special function 

 is unknown. Between the vessels around the pith may be seen 

 the rays of cellular tissue, which ultimatel}^ become hard and 

 firm, and which unite in bonds, never broken except by some 

 external force, the inside of the stem with the inside of the 

 bark. These rays make up the woof and have much to do 

 with the distinctive peculiarities of difterent sorts of timber." 



" Immediately outside the vessels inclosing the pith grows a 

 layer of woody fiber, upon which, in a more or less developed 



