BEITISH MOSSES. 25 



indicates, affects marshy situations, and often grows 

 amongst sphagnum, and as this is used for orchids, and 

 often kept in considerable heat, this form of the Aula- 

 comnium may sometimes be seen in orchid houses in great 

 abundance and beauty, raising its delicate heads above 

 the level of the sphagnum. 



The other form of the plant is double, i.e., the male 

 and female blossoms are produced on different plants; 

 the former is shown in Fig. 12, and the latter in 

 Fig. 13. This is a very handsome and strong-growing 

 Moss. 



The great diversity in the general appearance of these 

 two forms of the same Moss is very striking ; it suggests 

 the great influence of temperature on such forms, the 

 warmer temperature in this case producing the more 

 delicate plant and the colder temperature the more robust. 

 Furthermore, it is an instance of the correlation of great 

 difference of general form with differences of modes of 

 reproduction. 



Other Mosses produce gemmae on other parts of their 

 structure ; some on the midribs of the leaves, and some in 

 the axils. 



In the case of the Tetraphis there is reason to believe 

 that the cup that contains the gemmae is a modification of 

 a male flower, and from the drawing above presented of the 

 male flower of the Aulacomniu m (Fig. 12), it would seem as 

 if it had a tendency to produce the stalked heads of gemmae. 

 The drawing is a copy from one in Dillenius. I have 

 never seen such a growth in Aulacomnium, but the drawing 

 is probably accurate, and it suggests for investigation, as a 



