16 KANSAS UNIVERSITY SCIENCE BULLETIN. 



been inserted in full, since the writers hope that they may be 

 useful in future work on these plants, and since they believe 

 that the collection of carefully prepared statistical data of this 

 kind is very valuable for the decision of some biological ques- 

 tions. 



The writers wish to express their gratitude to W.C. Stevens, 

 professor of botany, for suggestions on the work, and to Hugo 

 Kahl, entomologist of the University of Kansas, for the identi- 

 fication of the insects. The drawings were made by Miss Mar- 

 guerite E. Wise. 



S. rostratum is a low, spreading, bushy annual, sometimes 

 attaining a diameter of four or five feet and a height of one and 

 one-half feet. 3 The pinnately lobed leaves, as well as other 

 parts of the plant, are beset with strong prickles. It seems to 

 be especially adapted to arid regions, thriving on the dry plains 

 of the Southwest. 4 



The material studied by the writers grew, for the most part, 

 in clayey soil, around old stone-quarries on Mount Oread, a pro- 

 jection of the Kaw river bluffs. A brief examination was made 

 of material growing in waste places in St. Joseph, Mo. 



During the very severe drought, which extended up to August, 

 S. rostratum was one of the few plants which were apparently 

 uninjured and blossomed with any considerable vigor. The 

 most of the observations were made after the drought was broken 

 by the rain of August 9, when the plants were in the height 

 of their flowering season. 



The flower has a somewhat irregular, wheel-shaped, gamo- 

 petalous corolla, bright yellow in color. Four of the stamens 

 are normal in their structure, but the fifth, which is on the lower 

 side of the flower, has attained a length almost twice that of the 

 others. Its anther is large and tapering. At about the middle 

 it is crooked a little toward the outside, and its slender, tapering 

 apex is curved upward. The filaments of all the stamens are 

 very short, bringing the anthers close up to the base of the 

 corolla. The small anthers are of about the same color as the 



3. One specimen observed growing in rich soil back of a feed-store in St. Joseph, Mo., 

 in early September had a diameter of over seven feet and a height of three feet. The plant 

 might be considered as normally developed, having produced apparently the normal number of 

 seed pods, and so would not bo classed with the rank vegetative development which plants 

 sometimes show when grown in very rich soil. 



I. fiT. roxtratum appears to be better adapted to xerophytic conditions by its extensive root 

 system than by any adaptation for the prevention of evaporation of water. When cut down on 

 a warm day, the plants wilt in a very few minutes. Roots extend down sometimes for more than 

 three feet, so that the plants generally appear perfectly fresh when others around are wilted and 

 drying up. 



