26 HUMPHREY 



The AnthocerotacejE are represented by Anthoceros fiisi- 

 JbrmiSy A. -pearsoni and A. ■phymatodes the first two being 

 very common, while the third, though not so widely distributed, 

 is very abundant in certain localities near Stanford University. 

 All three species are found growing luxuriantly in places of 

 severe exposure, though thriving best in slightly shaded locali- 

 ties. At one time it was supposed that A. fusiformis and A. 

 ■pearsoni were annuals but they were afterwards shown by 

 Campbell ^ to be perennial in habit. So far as the writer has 

 observed Anthoceros phymatodes survives through the agency 

 of its conspicuous tubers. In fact, it seems that virtually all of 

 the thallus dies during the dry season except these structures 

 which are packed with food-materials and serve as very effec- 

 tive water-storage organs. The other two species, while surviv- 

 ing the dry season, resume development with but a compara- 

 tively small amount of the old thallus persisting, though both 

 species are highly mucilaginous and especially adapted to 

 extreme conditions as described by Campbell.^ Careful exami- 

 nation of a large number of recently revived plants failed to 

 demonstrate the presence of sex organs even in their early 

 stages and it is probable that these develop after the new 

 growth of thallus is well under wa3^ With the exception of the 

 two species of Sphcerocarpus it has been shown that all of our 

 xerophytic forms are perennial, persisting from year to year 

 unless artificially interfered with. Just how extended a period 

 of desiccation they are capable of withstanding has never, so 

 far as I know, been determined. In the autumn of 1903 the 

 writer attempted to germinate spores of Fossombronia longiseta 

 that had been collected in 1896. Some of the old plants along 

 with the spores were placed in petri dishes containing distilled 

 water, while others were sown upon moist earth. None of the 

 spores germinated nor did the plants revive. The material was 

 sent me from an eastern herbarium and I do not know the con- 

 ditions affecting the material after collection. The failure of 

 the plants to revive and of the spores to germinate can throw 

 little light upon the question. 



'Campbell, 1904: Resistance of Drought bj Liverworts. Torreja, Vol. 4, 

 No. 6, p. 84. 



* Campbell, 1895: ist ed., Mosses and Ferns, p. 117; 2d ed., 1901;, p. 123. 



