SEASONS IN SOl'TIIERN ARIZONA 265 



Stems of the parasitic Citsciita, or dodder, make a rapid 

 growth during the humid season and quickly twine around 

 the stems and sink their haustoria deep into the bodies of 

 many soft seedlings, although also capable of attacking suc- 

 cessfully some forms with an indurated bark or epidermis. 

 During all of this season the humid air, especially after the 

 sudden rains, becomes laden with the pungent odors of the 

 creosote bush and of the various volatile substances produced 

 by many of the desert forms. 



Two species of Martynia, the unicorn-plant, spring up 

 in great abundance on the mesa-like slopes and 'in the alluvial 

 bottoms, the showy yellowish flowers being extremely deli- 

 cate, and enduring but a short time. The bifid stigmas are 

 highly sensitive to the touch, and when the inner surface of 

 either of the two lobes come into contact with any hard object 

 they quickly close together with a trap-like action which would 

 hold an ant or any small insect which might give such a 

 stimulus. The large double fruits are provided with curved 

 spines several inches in length, which readily clasp the foot 

 or hock of an animal and are thus carried long distances, 

 sometimes to the discomfort of the animal to which they 

 become attached. Long fibres are obtained from these fruits 

 by the Papago and Pima Indians which are used in making 

 the dark figures in basketry work. 



Two sunflowers {HeVuinthiis nun 11 us and H. petiolaris) 

 cover great areas in the bottoms, and the yellow disks of 

 the flowers continue to show until well toward September. 

 A small relativ'C of the morning glory, Evolvuhis, also 

 comes into action at this time, and germinating seeds with 

 the peculiar cotyledons of this family are abundant and 

 widespread. 



fVizIicenia sp. is abundant in low ground among the 

 mesquites, especially In places where the soil is slightly im- 

 pregnated with salt or with black alknli. The yellowish 

 racemes or cylindrical clusters of bright yellow flowers are 

 very striking, especially in contrast with the greenness of 



