PHYSIOLOGY AND MORPHOLOGY OF CALIFORNIA HEPATIC^ 29 



Of the above forms Fiuibriaria^ Targiotiia, and Porella are 

 the most sensitively hyj]jroscopic ; at least when moistened they 

 are the first to become turgid and resume activity. 



By dividing the total loss in weight due to artificial desicca- 

 tion by the air-dry weight we obtain in percentages the actual 

 fraction of the air-dry weiglit that is lost in drying. For exam- 

 ple it was found that Fimhriaria, lost 6.06 per cent, of its air- 

 dry weight while losses for the other five were : Targionia^ 

 12.3 per cent.; CryptomitrmDi, 5.86 per cent.; Rtccm, 8.47 

 per cent. ; Fossonibronia, 8.23 percent. ; Porella, 4.57 per cent. 



From these figures it will be seen that in the normal air dry 

 state, Targioni'a contains the greatest amount of the water of 

 constitution, while Fossombi'onia and Riccia contain about two 

 thirds as much. Poj-eUa, the only leafy liverwort used in the 

 experiment, had given up all but a very small percentage of its 

 air-dry weight followed closely by Cryptomit7'tum, one of the 

 Marchantiaceae. 



As a rule our summers are characterized by heavy morning 

 fogs which drift in over the mountains from the ocean. These 

 hang over the valley for three or four hours after sunrise greatly 

 reducing the temperature and leaving behind, each morning of 

 their occurrence, considerable precipitation, enough sometimes 

 to result in dripping from eaves. The past summer (1906), how- 

 ever, was unusuall}' free from these fogs, even late in the season 

 when ordinarily they are heaviest and most frequent. Fog- 

 less mornings are characterized here by slight or even no pre- 

 cipitation of dew and are forerunners of hot, extremely dry 

 days. During such a season as the one just described it is 

 probable that our liverworts remained in an absolutely dormant 

 condition. It has many times been demonstrated that all our 

 perennial forms on being moistened revive in from half an hour 

 to twelve hours, resuming growth very promptly if the supply 

 of moisture is constant. Campbell ^ has shown in a recent paper 

 that this peculiar adaptation is a property not only of certain of 

 the hepaticse but belongs also to Gymnogramme triangularis, a 

 fern common to this region, which dries up in summer, remain- 

 ing dormant throughout the season, without the resulting death 



' Loc. cit., p. 85. 



