Effect of Moisture on the Growth of Usneas. 71 



Here in Concord, Massachusetts, on a vegetable substratum of 

 average roughness (Pjr/*^-apple and pear), and in a climate of 

 periodic rainfall, amounting to about 40 inches per annum, 

 (maximum, August, 4.12 in.) and with a humidity of 82% 

 (maximum, autumn), two examples, one with a southern and 

 one with a northern exposure, showed that the greatest growth 

 was accomplished during the months of heaviest rainfall, and not 

 only by the plant with the northern exposure, but on the eastern 

 periphery of this plant. We might learn then, that moisture, 

 and cool shade are most favorable to such foliaceous lichens." 

 Since this paper was written I have completed a two year's 

 study of Usnea florida (L.) Web. with the same results. 



I have examined, during the past few years, nearly five 

 hundred Usnea specimens from the Pacific coast, and several 

 hundred from California, and I have yet to see a luxuriant 

 specimen of this genus from the "xerophytic forests" and 

 chaparral regions of the interior of California, an area to which 

 I never alluded. As to the wonderful growth of Usneas on the 

 great redwoods, where Mr. Herre says "here in California it 

 (Us. longissima) is ten or twelve feet long only in the redwood 

 forests" (1. c. 258), a California authority writes these Sequoia 

 forests occupy the"Coast ranges, where they are exposed to ocean 

 fogs, from the northern limit of the state to the southern bord- 

 ers of Monterey county, but are most abundant north of San 

 Francisco." Mr. Herre also speaks, himself, of the "fog chan- 

 nels and rain-laden wind currents of the Coast Range mountains" 

 (1. c. 257). 



I am free to admit that there are many causes for unusual 

 local growth of lichens that are still, and probably will be, a 

 sealed book to me, and that it might have been better to have 

 worded my sentence : seemed due in fact to abundant moisture. 

 The plate in Bull. Torr. Bot.Club, 37: PI. 3 Fig. 4, 1910)will show 

 the "robust" * luxuriance to which I referred, a condition 

 that I cannot think any undisturbed Usnea growing in the past 

 primeval forests of the eastern states ever exhibited, even before 

 the arrival of the white lumberman. 



As I have already remarked elsewhere, western coast Us- 

 neas show a paler and more stramineous coloring as compared 



♦Diagnostic word used in Mr. Herre's original description of t/i. Californica. The word 

 "bulkiest" was also used. (Proc. Wash. Acad. Sci. 7:34-5. 1906). 



