20 HICKS, ON GONIDIA OF LICHENS. 



at the base will be seen the latter changing into a small 

 thallus — a squamule. 



I have kept patches of Chlorococcus from the neighbour- 

 hood of Cladonia on the bark of trees and under glass till 

 soridia appeared, and then it became in CA-ery respect a mass 

 of Gleocapsa. I have never found Cladonia pyxidat a without 

 it, except in very dry situations ; but when they were removed 

 to a moist atmosphere the Gleocapsa appeared. The Chloro- 

 coccus from heathery places, where Cladonia alone grew, 

 always produced the same results. 



Besides the origin of Gleocapsa, Palmoc/lcea, Sorospora, 

 &c., from the soridia, and besides the mode set forth by H. 

 Sachs, there is another way in which the above organisms 

 spring from Cladonia. In this latter the whole of the goni- 

 dial layer of the thallus sometimes becomes converted into 

 them ; the finest masses of Palmoglcea I have met with came 

 from this source. In this condition the mucous layer of the 

 cells is at first of small thickness, and more or less angular 

 bj^ mutual compression (being much as is seen in Palmella 

 cruenta, only of a green colour) , but as segmentation proceeds 

 they overcome the resistance, expand, and become more 

 globular. The resulting forms are then as I have above de- 

 scribed as arising from the soridia. In some I have noticed a 

 condition precisely like thatof Hassall's Coccochloris variabilis. 

 When all the gonidia of a thallus assume the Gleocapsa 

 change the separate masses of each variety are of larger 

 extent, but they even then are so blended as to preclude any 

 doubt as to their common origin. In Plate II, fig. 18, I 

 have shown a portion of these masses. 



The felted fibres are more or less mingled with the Gleo- 

 capsa and other forms, and their presence in a mass of 

 unknown origin will indicate its parentage. 



It will be readily seen from the above observations that 

 these facts have an important bearing upon the independent 

 existence of manj^ of the unicellular algaj. 



In the accompanying plate will be obserxed almost every 

 form of what has formerly been called Hcematococcus, Agardh, 

 and more recently Gleocapsa, Iviitzing. All these forms 

 have been named as distinct species, but hoAV unsatisfactorily 

 so I leave the best observers to testify. 



If it be a fact, as appears to me very evident, that all 

 these forms can and do arise from one cell, then their 

 existence as distinct species and genera is at an end, and 

 in this I go further than Sachs, and consider that we must 

 exclude Coccochloris, Spv. [PalmoglcEa, Kiitzing), (for the 

 growth found after immersion or in very damp situations pos- 



