APPENDIX D. Iv 



in Cladofiia pyxidaia, though similar processes have been 

 watched in connection with the gonidia of other Lichens 

 belonging to the same and to different genera. 



When growing in a dry situation (or if the season is hot 

 and dry) the gonidia of Cladojiia pyxidata behave in the 

 same manner as those already described of Parmelia and 

 Chlorococcus ; but, on the contrary, if the weather becomes 

 damp, if the plant grows in a damp situation, or even if 

 removed to one, then other and quite different changes 

 ensue. 



Under any one of such circumstances, Dr. Hicks says : — 

 ' The first change observable is that some of the segments 

 become enveloped by a layer of mucus, inside of which sub- 

 division still further proceeds, the portions in most cases pos- 

 sessing, after a little time, each a separate mucous envelope ^ 

 Thus we have all the elements of a Gleocapsa (Kiitzing) 

 growth. At first, commonly, the subdivision is continued on 

 the binary plan, which may continue for some time.' Other 

 modes of subdivision, however, may follow. The early seg- 

 ments may separate from one another, each provided with 

 a mucous layer, but in others the mucous envelope of the 

 original cell does not dissolve away, though segmentation pro- 

 ceeds in its interior. Thus masses result, in which the Gleo- 

 capsiform cells have from one to three common envelopes, 

 and a condition is produced, as Dr. Hicks points out, similar 

 to HassaFs Hematococcus rupesiris. But, he says : — ' In the 

 same mass — the produce of the Cladoma-?,ov\<X\2i — will be 

 found every variety of subdivision, each form constituting 

 a mass of a greater or smaller extent,' though these 

 various products were not always indiscriminately mingled, 

 * as if a particular kind having once commenced, it would, 



^ All the changes which are now being described are accurately 

 represented in PI. ii. of the ' Journ. of Microsc. Science' for i860. 



