2 20 The Living Plant 



such cases the obstruction in the bark causes an accumulation 

 of the food just above, with a resultant swelling of the tissues 

 that often is very prominent. The same thing happens also 

 naturally where a twining stem, such as that of a Bittersweet, 

 tightly constricts a growing tree, in which cases the swelling stem 

 always shows a very much greater enlargement above than below 

 the vine. 



Such is the method whereby food materials are transported 

 from their places of formation to the places of storage ?nd use. 

 The same general method explains the transport and accumula- 

 tion of all those special substances, usually of definite and adapt- 

 ive functions, which we call secretions, — the volatile oils, nectar, 

 some coloring matters, and others which have been considered 

 in the chapter on Metabolism. 



This is really the place to bring this particular chapter to a 

 natural conclusion ; and it is truly a pity that it cannot be done. 

 For somewhere in the book we have to consider the prominent 

 subject of the cellular anatomy of stems, and this is the most 

 suitable place. However, the matter is not indispensable to a 

 clear understanding of the chapters that follow, and therefore 

 the reader may skip the remainder of this chapter if he wishes. 

 And if the said reader should ask why I do not skip it myself, I 

 would answer that the integrity of my subject requires its pres- 

 ence. For with regard to this book I feel with Nehemiah Grew, 

 who wrote more than two centuries ago in the dedication to his 

 great work on the Anatomy of Plants, — ''Not I, but Nature 

 speaketh these things." 



If, accordingly, in pursuit of a knowledge of the anatomy of 

 stems, one cuts with a sharp knife a clean section across any 

 young stem, he can always discover the ends of the fiber-like veins 

 distributed in a uniform ground-work of tissue. And if, further- 

 more, he makes a thin section from a typical young stem, such as 

 Castor Bean, and magnifies it moderately, he will have before 

 him such an appearance as is pictured herewith (figure 73). 



