62(3 



THE NATIONAL GEOGRAPHIC MAGAZINE 



Though of all plants the most common, 

 the grasses are of all common plants the 

 least known. 



The story of the grasses begins long 

 before the age of man. In the geologists' 

 Book of Nature, there are records of 

 grasses that gladdened the face of the 

 earth in the days of the tiny eohippus, 

 from which the horse is sprung. 



Some of the grasses have served man 

 so long and in turn have been served by 

 him that they have become as powerless 

 to live without him as he is unable to get 

 along in comfort without them. Imagine 

 corn and wheat fighting their own way 

 through the years. How soon they would 

 fail without a plow and a harrow and a 

 cultivator to prepare their beds and fight 

 their battles with the weeds. 



But other grasses have fought for 

 themselves so many generations that they 

 ask naught of any one. These travel 

 along the roadsides of the world, sending 

 their seeds hither and yon, until they have 

 effected a foothold by ''peaceful penetra- 

 tion" in a thousand communities. 



HOW GRASSES SEND THEIR SEED ABROAD 



The bur grass sends its thorny seed 

 burs far and wide, attached to some pass- 

 ing animal or human being. The terrell 

 grass produces seeds encased in cork-like 

 hulls, which float to new fields on the 

 waters of the brook beside which it 

 grows. Couch grass grows from the root 

 as well as from seed, and sends its spear- 

 pointed rootstalks up through many a 

 new foot of soil. 



The beach grass has long since learned 

 the tricks of the sand in attempting to 

 bury all that would bind it, and has 

 worked out a plan for circumventing the 

 resourceful wanderer. It rises out of the 

 sand as fast as the dune can build itself 

 up, and at the same time sends its roots 

 downward until it clinches the dune to 

 solid earth. 



Many grasses spread like the couch 

 grass, by runners or rootstocks, having a 

 succession of joints, from each of which 

 arises a shoot that shortly takes root on 

 its own account and in its turn sends out 

 other runners. 



Others develop only fibrous roots, and 

 usually, like orchard and panic grasses, 

 are found in bunches or tufts. 



The seeds of some species are unde- 

 stroyed and undigested by the animals 

 that feed on them and get their chance to 

 build a new colony through these carriers. 



GRASS SEEDS WITH BARBS 



Some other kinds of seeds are pro- 

 vided with novel weapons for forcing 

 themselves into the soil. They have a 

 prickly callus which bears stiff hairs 

 growing away from the point like the 

 barbs from the arrow's head. Once the 

 prickly point has penetrated the soil, to 

 draw it out is difficult, since the stiff 

 hairs, rubbed the wrong way, interpose 

 a strenuous objection. 



A strong, bent contrivance, known as 

 an awn, and twisted like a rope, is used 

 by some grasses to bury their seeds in the 

 ground. The rope-like twist is influenced 

 by dampness and dryness — it uncoils 

 when damp and coils again when dry. 

 This acts as a motor to drive the seeds 

 into the ground. 



In high latitudes and corresponding 

 altitudes, where the ripening of the seeds 

 is uncertain, entire spikelets are trans- 

 formed into leafy shoots, provided at the 

 base with rootlets ready to grip the 

 ground and grow wherever they fall. 



What wonder that, in view of all these 

 devices, one feels like saying of them as 

 Darwin said of the schemes to which the 

 plants resort in order to insure cross- 

 fertilization : "They transcend in incom- 

 parable degree the contrivances and adap- 

 tations which the most fertile imagination 

 of the most imaginative man could sug- 

 gest, with unlimited time at his disposal." 



WHY GRASSES HAVE JOINTS 



Every one has noted what are popularly 

 known as the "joints" of grass, but which 

 are technically described as "nodes." Their 

 mission is not, as most people believe, to 

 give strength to the stem, but rather to 

 help it always to stand upright. 



The cells of these "nodes" are known 

 as "geotropically sensitive" — attracted to 

 the earth or driven from it. A wind 

 comes along and bends the grass, so that 

 it becomes unable to resume its upright 

 position. Thereupon the cells in the 

 "node" on the side of the stem that in- 

 clines toward the earth begin to lengthen, 

 thus, by imperceptible degrees, lifting the 

 stem to its upright position again. 



