208 THE PLANT WOELD. 



whicli the moving awns brace, which action by degrees forces the 

 seed into the ground. 



In order to observe more f nllj these hygroscopic movements, 

 the writer camped for several days in the vicinity of large 

 alfilaria patches about Oracle, Arizona. At the close of a dry, 

 hot day the awns Avere coiled tightly in the usual spiral manner, 

 thus giving a nominal coherence to the abundant seed masses. 

 The next morning at 4 :00 o'clock, tlie formation of dew having 

 been copious, the awns Avere everywhere observed uncoiled and 

 pliable from the large amount of moisture taken up. With the 

 rising temperature of the morning, the moisture being gradually 

 dissipated, tlie hygroscopic movements of the awns became ap- 

 parent, at first slow, later very active so as to give to the seeds 

 curious, twisting or -writhing movements. About noon this came 

 by degrees to a close, leaving the seeds in about the same con- 

 dition as on the previous afternoon. Thus continued, from day 

 to day, the interesting process of seeds actually planting them- 

 selves. "^ T. T. TI-IOKIv^r>Eru 



The Universitv of Arizona. 



NOTES ON SPIDER-FLOWERS. 



Some years ago when botanizing on the high plains of 

 western Kebraska in a period of very liot, dry weather, wlion 

 many plants were more or less wilted on account of the lack of 

 moisture in the soil, I noticed the peculiar appearance of plants 

 of the common Spider-flower (Cleome serrulata). The branch- 

 ing stems of this species bear trifoliate leaflets upon petioles of 

 considerable length, the leaflets normally spreading at the sum- 

 mits of the ascending petioles. Now, under the stress of a scanty 

 water sup])ly, these leaflets, instead of falling limply in wilting, 

 actually stood up erect. That is, this plant wilts up instead of 

 doivn. 



Another species (C. spinosa) is remarkable for the great 

 length of its stamens, which are often from four to six or more 



