138 MASSACHUSETTS HORTICULTURAL SOCIETY. 



dry, light, and powdeiy, and .easily blown about by the wind, 

 and cross-fertilization among grasses is effected by this agency. 



If the variety in the external form of grasses is Avonderfully 

 great, their internal structure is scarcely less so, and the histo- 

 logical studies of grass stems, leaves, and fruits are exceedingly 

 interesting. Intricate problems in mechanics are exhibited in the 

 structure of the slender cylinders which constitute the grass stem, 

 and which, in many cases, possess a strength most surprising. 

 The amount of mechanical tissue entering into the structure of 

 the stem which holds a heavy head of wheat is insignificant, but 

 the disposition of the various elements of this tissue gives it the 

 strength necessary to perform its proper functions. Again, the 

 leaves of grasses, which many think so much alike that they w^ould 

 consider the expression " as like as two blades of grass " as forcible 

 as the more common phrase " as like as two peas," exhibit a di- 

 verse and marvelous interior structure. No more delicate trac- 

 ings or beaiitiful designs of lace work can be imagined than are 

 l^resented by these same grass leaves when viewed under the 

 microscope. The designer might well study these tissues, for in 

 them he would find many new figures and combinations of lines, 

 the beauty of Avhich he could not hope to excel, and the repro- 

 duction of which could not fail to receive the liighest admiration. 

 In their internal structure as in tiieir outward contour, the leaves 

 of grasses present such definite characters that these may be 

 used to distinguish species. A minute transverse section of the 

 leaf of Kentucky Blue grass, which one could barely see with 

 the naked eye, would, under the microscope, present characters 

 which at once distinguish it from all other grasses. They are 

 totally different from those exhibited by a leaf of Orchard grass, 

 and these again are Avholly unlike those of Meadow Fescue. 

 There are certain cells in the leaf tissue, running from the base 

 to the summit, which are larger and have thinner walls than the 

 surrounding cells. These special cells readily absorb or give up 

 moisture, and because of this property they exercise tlie meclmni- 

 cal function exhibited in the expansion or opening out of the 

 leaves, or their contraction and rolling together. 



The provisions Avhich nature has made for the distribution of 

 grasses is an interesting subject, and one worthy of passing 

 notice. In many cases the seeds are covered with delicate chaff- 

 like scales, or are furnished with winged or feathery appendages, 



