53 



upon wliich it occurs being of course that of Physcomitrella 

 patens: 



Physcomitrella patens 9 X Physcomitrium turhinatnm d^. 

 Sporophyte altogether about 2.5 mm. high, the capsule exserted 

 upon a seta longer than itself. Vaginule swollen at base, abruptly 

 contracting to the base of the seta ; the latter strongly pigmented 

 dark brown in its lower M~H> above green, about 1.25 mm. to 

 the base of capsule. Capsule pyriform with neck fairly long and 

 contracting gradually into seta, about twice as high (i mm.) as 

 wide, blunt at apex, light yellow in its immature condition. 

 Stomata rather few at base of capsule, of normal Funariaceae 

 type with completely coalesced guard-cells, pigmented yellow, 

 nearly round, about 35 ^ in diameter. Exothecial cells nearly 

 rectangular to slightly pentagonal or hexagonal, arranged in 

 definite latitudinal zones, thin-walled, about twice as long as 

 .wide (50 X 25 /i), lid not clearly separated, but exothecial cells 

 in upper part of capsule somewhat abruptly shortening, so that 

 their length does not exceed their width, also slightly thicker- 

 walled and more strongly pigmented yellow. Spores formed, 

 but entirely immature. 



As the material was collected in November shortly before the 

 breaking of winter, and Physcomitrella patens is apparently an 

 annual, it is rather doubtful if any of the hybrid capsules matured 

 their spores, and unfortunately no attempt was made to mature 

 them indoors. The whole matter of moss-hybrids is relatively 

 uninvestigated. They have been noted most frequently, in fact 

 almost exclusively, in Europe, whose moss-flora has been more 

 intensively studied. Even there the only cases of hybrids which 

 are well substantiated are those between cleistocarpous forms 

 with sessile capsule and the related forms with seta and more 

 highly' organized capsule, the intermediate capsule being in these 

 cases distinct enough to readily attract attention. Such hybrids 

 have been described in the series Pleuridium-Ditrichum, Asto- 

 mum- Weisia- Trichostomum and Physcomitrella- A phanorhegma- 

 Physcomitrium. Whether the hybrid spores can produce new 

 plants and what the nature of such plants might be is, so far as 

 I am aware, entirely unknown, so that speculation as to what 



