6i2 MOSSES AND FERNS 



single tier of well-defined chambers, each opening at the surface by a 

 pore. In most of these (see Fig. i8*) the green tissue consists for the 

 most part of short filaments growing from the floor of the air-chamber. 

 The free ends of these filaments, especially immediately under the 

 pore, are often colorless, and more or less enlarged. This is especially 

 conspicuous in Fegatella (Cavers (6, 9) ). 



The epidermal cells surrounding the pores keep pace with the growth 

 of the thallus, so that the pores remain of nearly their original size. 



P. 49. Ernst (2) has more recently described the structure of the 

 thallus in Dumortiera trichocephala, collected in Java, and also of a 

 second species, D. velulina, in which the remains of the dorsal 

 lacunse are conspicuous. Wiesnerella is a genus evidently related to 

 Dumortiera, but having a well-developed epidermis with pores opening 

 into the air-chambers. 



P. 56. Cavers has made a careful comparative study of the carpo- 

 cephalum in several genera of the Marchantiaceae and concludes that 

 in all of them, except Clevea and Plagiochasma, the carpocephalum is 

 of the composite type. He believes, however, that the Astroporae of 

 Leitgeb represent a natural group, and to a lesser extent this is true 

 of the Operculatae, although the limits between the latter and the 

 Compositae are not at all definite. 



P. 58. Cryptomitrium also occurs in the Himalayas. 



P. 60. In a recent paper by Miss O'Keefe (i), the young embryo 

 Targionia is described as having two transverse divisions before any 

 longitudinal ones were formed — i.e., there was not the quadrant forma- 

 tion typical of the Marchantiales. The writer's preparations of the 

 young embryos showed the normal quadrant division (see Fig. 23), 

 and it would be interesting to know whether Miss O'Keefe's specimens 

 were abnormal, or whether possibly they were specifically different 

 from the California plant. Meyer (4) shows that in Plagiochasma 

 the young embryo consists of a row of four cells. 



P. 65. In Dumortiera trichocephala, and in the allied genus Wies- 

 nerella, there is a very evident seta, and in Monoclea it is very much 

 elongated. 



P. 69. Cyathodium is represented by several species in the warmer 

 parts of the world. The largest and least reduced species is C. 

 foetidissimum, widely distributed through the Malayan region, where it 

 occurs sometimes in great abundance in shallow caves, or on deeply 

 shaded rocks. The delicate thallus appears to glow with a green 

 phosphorescence when seen at a certain angle, this being apparently 

 due to the form of the superficial cells, which reflect the light strongly. 



