PROCEEDINGS OF THE ANNUAL MEETING. 137 



cast off, in case of trees, by a small joint, and drop to the ground, serving 

 as a protection to the roots and bed for the tender seeds till the approach 

 of spring. 



The following table is from "How crops feed," by Professor Johnson of 



Yale: 



TABULAR VIEW OF THE RELATIONS OF THE ATMOSPHERIC INGREDIENTS TO 



THE LIFE OF PLANTS. 



Oxygen, by roots, flowers, ripening fruit, and by all growing 



parts. 

 Carbonic acid, by foliage and green parts, but only in the 

 light. 

 Au u /I K I + J Ammonia, as carbonate, by foliage, probably at all times. 



Absorbed by plants i Water, as liquid, through the roots. 



Nitrous acid-- { United to ammonia, and dissolved in water 

 Nitric acid } through roots. 



Ozone Uncertain. 



Marsh gas S 



Not absorbed bv nlants -^ Nitrogen (in a free state). 

 JNot absorbed by plants. ^ ^y^^^^. j^ ^ ^^^^^ ^^ ^,^p^^_ 



Ozone^'V ( ^^ foliage and green parts, but only in the light. 



Exhaled by plants ■{ Marsh gas in traces by acquatic plants (?). 



I Water, as vapor, frord surface of plant at all times. 

 [Carbonic acid, from the growing parts at all times. 



PECULIARITIES OF LEAVES OF GRASSES. 



The leaves of grasses are marvelous structures and most admirably 

 adapted for self-preservation and renewal when grown among grazing 

 animals. After it becomes fairly started, the blade elongates by multipli- 

 cation of cells just at the base, where it leaves the main stem. The tips 

 may again and again be nipped off, but the blade continues to be pushed 

 up by growth from below. I have a leaf of June grass, taken from a hedge 

 where it was protected, that is five feet four inches long. 



Again, in dry time, the leaves of June grass and leaves of many other 

 kinds of grass, fold up lengthwise like closing the two halves of a long, 

 narrow, open book. Near the mid-nerve on either side of the upper sur- 

 face of the blade is a group of thin-walled epidermal cells extending 

 deeply into the leaf its entire length. These cells are very sensitive, and 

 with loss of moisture contract, causing the blade to close as above men- 

 tioned. When moistened, they expand, spreading upon the blade. The 

 blades of orchard grass open and close in a similar manner, only the deep, 

 thin-walled cells are limited to one narrow band just above the mid-nerve. 

 Some leaves, like those of timothy and Indian corn, roll in from both edges 

 like the two sides of a scroll. This is caused by numerous longitudinal 

 strips of thin-walled cells on the upper side, all of which, acting together, 

 in dry weather, roll the margins in instead of closing them in the manner 

 mentioned for June grass and orchard grass. This closing of the blades 

 in a dry time is a means of self protection to the plant as the surface 

 directly exposed is reduced one half. 

 18 



