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an uncertain and scanty water supply, permits them to flourish 

 in situations far more arid than most ferns can endure. Those 

 only which have this habit are able to exist in the desert region. 

 They have their fronds protected against the heat and too rapid 

 evaporation by a clothing of hairs or scales, or by a powder or a 

 viscid secretion, only one, Cheilanthes Calif ornica, being naked, 

 and so needing a moister place than the others. 



Their time of growth is the rainy season, and at its conclu- 

 sion the fronds in place of dying, coil themselves into tight balls 

 or looser bunches, the spore-bearing lower surface innermost. 

 They are now dry and brittle, and if gathered, crumble into frag- 

 ments. Apparently they are dead, but at the first rainfall they 

 are softened, unroll, and take up again the interrupted functions 

 of life. So long as the moisture lasts they continue to grow ; when 

 it fails they resume their dormant state, and this alternation of 

 growth and rest may occur more than once in a season. There is 

 a colony of Notholccna cretacea on the exposed slope of a lime- 

 stone hill so near me as to be conveniently visited. The crevices, 

 in which the plants of this colony grow, are narrow and shallow 

 so that they cannot long retain moisture. So in Winters of defi- 

 cient precipitation, when the rainstorms are succeeded by inter- 

 vals of drying winds Notholcrna changes from growth to rest, 

 and back from rest to growth full half-a-dozen times in as many 

 months, and one knows from the state of the atmosphere whether 

 their fronds will be found expanded in growth or dry and thrust 

 up like rows of little white or yellow fists. 



The fronds of all these ferns retain their vitality until they 

 mature their spores; they then die, and the withered ones long re- 

 main as a protective cluster around the living ones. Some of the 

 earliest fronds may ripen their spores the first year in good sea- 

 sons, but probably the most do not bring them to maturity till the 

 second winter. 



The ferns which possess this ability of suspending and renew- 

 ing the active functions of life are Gymnogr amine triangularis, 

 Notholcena cretacea, N. Newberryi, N. Parryi, N. tenera, 

 Cheilanthes Calif ornica % C. Cooperce, C. Clevelandii, C. fibril- 

 losa, C. myriophylla, C. Parishii and C. viscida. Pellcea orni- 

 thopus and P. andromedcefolia become dry and brittle, but do 

 not coil up their fronds. Besides the Southern California ferns 

 here mentioned this peculiar adaptation is common in ferns of 

 other arid regions. 



