THE KANSAS UNIVERSITY 

 SCIENCE BULLETIN. 



Vol. VII, No 8] JUNE, 1913. [r.^xvirNH 



HISTOLOGY OF JANUSIA GRACILIS. 



BY B. J. CLAWSON. 



Plates XXII-XSVIII. 



(Contribution from the Botanicnl Laboratory.) 



JANUSIA GRACILIS was one of the plants collected by 

 the University of Kansas from the desert region of Ari- 

 zona by Mr. Peace. It was collected in the year 1908 in 

 the vicinity of Tucson, Ariz., from Tumamoc Hill, on which 

 the desert laboratory stands. There are four topographical 

 divisions found in this desert region : mesa land, river bot- 

 toms, rocky slopes of mountains, and draws in these moun- 

 tains. Of these four the rocky slopes of the mountains are 

 the dryest. It seem_s that this plant is one of those best fitted 

 for the dry, hot conditions, since it survives upon these slopes 

 where the soil is just thick enough to cover the rocks, which 

 are broken so that what moisture the soil could collect from 

 the rain is soon drained away. 



A short description of the genus Janusia is given by 

 Bentham and Hooker. Gray mentions both the genus and 

 species in his catalogue of North American Plants. Not even 

 the family to which the genus belongs is mentioned in the 

 seventh edition of his manual. Engler and Prantl give a de- 

 scription of the genus similar to that given by Bentham and 

 Hooker. They also mention the species, saying that it is found 

 in Mexico. 



The material studied was an average of that found upon the 

 field, and was a slender, twining, woody shrub. In no place 

 had it reached the thickness of one centimeter. 



Received for publication October 8, 1912. 



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