722 



SCIENCE. 



[N. S. Vol. XIV. No. 358. 



that we have here a natural color-scheme in 

 which the plant formations are mapped on 

 the landscape. Let me attempt to repro- 

 duce some of the color pictures I have seen. 



First, give the picture a general gray tone, 

 which may include the sky as well as the 

 earth surface. In the background where 

 the hills slope away to the horizon are great 

 patches of dull red or purple, bordered by 

 the silvery gray of the buffalo grass. 

 Here in the foreground may be a stretch of 

 light yellow marking the area of a field of 

 maize stalks still standing where they grew, 

 and there may be a gray, velvet-like 

 meadow of buffalo grass, with dashes of 

 brick-red now and then on its surface where 

 the bunch grasses stand, or where the red 

 stems of the knotweeds mark the winding 

 course of a ' draw.' Here and there the 

 landscape shows a black spot where the 

 farmer has plowed up the rich soil in readi- 

 ness for the spring's plantings. Crossing a 

 ravine we find the sloping sides red with 

 the bunch grasses, below which is a belt of 

 yellow ' prairie grass ' bordering the dry 

 bed of the brook, the latter marked here 

 and there with red-twigged willows. In 

 the distance, where a stream winds its way 

 along, is a black line of cottonwood trees, 

 whose trunks and larger branches show 

 black against the gray background, and on 

 nearer approach we note the silvery sheen 

 of their twigs contrasting with their dark 

 stems and branches. A plum thicket in a 

 ravine forms a dark-blue patch, with a 

 background of dull red knotweeds, or bunch 

 grass, further back shading into the silvery 

 gray of the buffalo grass. 



Now we see a silvery gray meadow of 

 buffalo grass with faint patches of reddish 

 color scattered over it ; back of it a fringe 

 of cottonwood and box elder trees with dark 

 trunks, the latter loaded with their light 

 brown fruits, and still back of these the 

 slopes with alternating silvery gray patches 

 of buffalo grass and the dull red of the 



bunch grasses, running up to the sky line 

 of light ochre where a field of maize is still 

 standing. To complete the picture add a 

 few stacks of alfalfa, now dark brown or 

 black, and a spectral windmill here and 

 there outlined in somber colors. 



Allow me to show you one more picture 

 seen near Minden, under the ninty-ninth 

 meridian. Here is a little valley framed 

 in with a brick- red border of bunch grass 

 which grew on its sloping sides : next to it 

 are patches of yellow switch grass and sil- 

 very gray buffalo grass, and a rich, velvety 

 maroon spot where the ripe fruits of the 

 smooth sumach give their color to the 

 scene. The floor of the valley is covered 

 with the red knotweed whose red is deep- 

 ened in a central strip to a rich purple- red 

 where a water course has encouraged the 

 red- stemmed Polygonums to grow. 



I need not attempt to place before you 

 more of these general views. In all cases 

 the picture has a basis of gray, and on this 

 are laid reds, yellows, blues, purples, 

 browns and blacks, etc. Let us inquire 

 into the meaning of these strips and patches 

 of color. 



When the autumn drought and the early 

 winter frosts stop the growth of vegetation 

 the green shades of summer, themselves by 

 no means uniform, are replaced by the hues 

 indicated in the preceding paragraphs. 

 The practiced eye can distinguish the plant 

 formations on the open plains by their shades 

 of green when the vegetation is in its vigor, 

 and it appears that the early winter colora- 

 tion is in a measure related to this fact. 

 The boundaries of the formations are more 

 sharply defined in the early winter, since 

 the color differences are emphasized. I 

 have not, however, been able to determine 

 any law Of color change in the plants of 

 different formations. In fact it appears 

 that each plant is a law unto itself. Thus 

 the light green of the low bunch grass 

 (^Andropogon scoparius) gives place to a red, 



