180 THE POPULAR SCIENCE MONTHLY. 



voluntary celibacy for those who overtax their vital energies by an 

 intellectual strain that hurts the offspring ; and in the honoring of 

 those lighter and easier methods of making money which have hitherto 

 condemned a woman to social ostracism, and denied her the status she 

 deserves and has inherited. — Fortniglitly Review. 



ENEKGY IN PLANT-CELLS. 



By Peofessor T. H. McBEIDE. 



FEW people have any true conception either of the kind or amount 

 of actual energy displayed in the life and growth of a simple 

 plant. In ordinary experience the manifestations of vital energy are 

 always associated with the activity of some animal. Life in the ani- 

 mal seems at its best ; its forces are more concentrated, hence more 

 vivid in display, and in every way appeal more certainly to our atten- 

 tion. An animal can move, can exhibit strength, can do work, hence 

 has force, exhibits energy — vital energy, if you please. But in the 

 plant-world these forces are less noted, although going on in much the 

 same way to the accomplishment of life's purposes ; and, if less obtru- 

 sive in their action and simpler in behavior, are also less difficult to 

 study and easier to understand. To see where some of these forces 

 are exerted, how they are manifested and how controlled, is, in so far 

 as circumstances may allow, the purpose of this article. 



The most patent display of energy on the part of a plant is in con- 

 nection with the growth. Every one knows how a growing seed will 

 send a shoot to the surface through a hard covering of overlying earth. 

 And above-ground the tip of the growing plantlet persistently defies 

 gravitation. Roots find their way through the interstices of clay, and 

 crowd into the enlarging crevices of rocks. The bark of a tree, under 

 tension, in equilibrium of pressure and resistance as long as the tree 

 lives, evinces an energy very appreciable in amount. The amount of 

 force concerned in this case we are not left to imagine, but may at 

 least approximately estimate. 



Along the highway that passes one of our Iowa farms were planted 

 many years ago a row of soft-maple trees, designed to serve at length 

 as posts for carrying the wires of the fence. When the trees attained 

 suitable size they "were put to the use intended by nailing to each tree 

 a piece of pine lumber four feet long and two by four inches in sec- 

 tion for the better attachment of the wires. Since the erection of the 

 fence in the way indicated, the growth of the trees has produced some 

 very striking results. The blocks were attached to the trees by heavy 

 iron spikes (Fig. 1). These seem to have rusted into the tree, and by 

 their points to have held firmly, while by the continual deposition of 



