Vol. 4 No. 6 



TORREYA 



June, 1904 

 RESISTANCE OF DROUGHT BY LIVERWORTS 



By Douglas Houghton Cami'Ijei.i, 



\Ve are accustomed to consider the archegoniates in general 

 as moisture-loving plants, and this is, to a certain extent, true. 

 But it readily may be shown that there are many exceptions to 

 the rule, even in regions of abundant moisture ; while in more 

 arid districts it is becoming clear that many species have developed 

 special contrivances for surviving long periods of drought. 



In moister regions, like the eastern United States, many species 

 of rock-haunting or epiphytic mosses occur which can survive a 

 certain amount of desiccation ; and among the Hepaticae may be 

 mentioned various foliose Jungermanniaceae which share this 

 peculiarity with the mosses. How far this power of resisting 

 drought is found among the eastern thallose Jungermanniaceae 

 and Marchantiaceae, so far as the writer is aware, has not been 

 investigated. 



For a number of years the writer has been interested in the 

 archegoniates of California, especially the hepatics, and his 

 attention has been directed repeatedly to the power shown by 

 nearly all the species of resisting the long dry season which 

 regularly prevails each year. In the region around San Fran- 

 cisco Bay, the dry season generally lasts from about the middle 

 of May until late September or early October. Sometimes for 

 fully six months no rain at all falls. This was the case in 1903, 

 when from mid-April until October there was no rain at all, and 

 not until November was the rainfall enough to start vegetation. 

 Nevertheless, the growth of Hepaticae during the present season 

 has been very luxuriant, and there is no evidence of any harm 

 having resulted from the unusually protracted drought. In the 

 bay region, however, there is seldom the excessive summer heat 



[Vol. 4, No. 5, of ToRREYA, comprising pages 65-So, was issued May 13, 1904. J 



81 



