LINDSAY, ON POLYMORPHISM IN LICHENS. 11 



described as various genera oi Alg(B [e.g. genera Protococcus, 

 Chlorococcus, H(Bmatococcus, Coccochloris, Glceocapsa, Pal- 

 moglosa, Sec). Kiitzing long ago affirmed that the Lichen-goni- 

 dium might be developed into an Alga or Lichen, according to 

 the external influences to which it Avas exposed. I am not in a 

 position to confirm his observations, because I have not my- 

 self watched the development of the gonidic cell under the 

 varying conditions referred to. But I have sufficiently 

 studied gonidic development in Lichens to admit at least the 

 probable correctness of Kiitzing's view; while I have no 

 doubt of this fact, that the cells which constitute a certain 

 stage of development of certain Alga, Lichens, and Mosses, 

 and which are generally known as forms of the typical 

 Lichen-gonidium, are indistinguishable, if they are not iden- 

 tical. 



The subject is one to which I hope to give attention at 

 some future time, by growing the Lichen-gonidium artificially, 

 and watching its gradual development under different condi- 

 tions of warmth and moisture, or their negatives. These ex- 

 periments, I trust, will be connected with a comparative 

 series by Chas. Jenner, F.R.S. Edinb., on certain of the so- 

 called Unicellular Alga.* Meanwhile, I may direct atten- 

 tion to the suggestive papers of Dr. Hicks, on the ' Gonidia 

 of Algae, Mosses, and Lichens,' in this Journal, f and in the 

 'Transactions of the Linnean Society, 'if papers which contain 

 some very interesting results of similar series of experiments. 



Among minor forms of polymorphism may be mentioned 

 — 1, different forms of sporidia ; 2, differences in the number 

 of sporidia, in the same apothecium or sj^ecies. For instance, 

 quite recently Carroll records a var. heterospora of Lecanora 

 sophodes, Ach.,§ which, he says, "is remarkable for having 



* Mr. Jenner writes me (November, 1867) — " The subject is . . . . 

 one of the most subtle in nature, and one the exposition of which is only 

 possible by laborious and well-considered methods oi germination .... 

 There is no more interesting or important study connected with Natural His- 

 tory than that arising from the influence of circumstances on the develop- 

 ment of the simpler forms of life. Early vegetable life, being more simple 

 and facile of investigation than animal forms of life, renders it, in our present 

 state of knowledge, the more valuable of the two. . . I have no doubt 

 at all myself as to the transmutation of species ; but the evidence that is 

 ample to satisfy the individual worker is insufficient to establish a fact, which 

 is at variance with principles of thought that rule the world .... I 

 shall gladly join you in experiments on germination ... I scarcely 

 doubt some important results may be eliminated." 



t ' Quart. Journ. Mic. Sci.,' 1860, pp. 239 ; 1861, p. 15, 90. 



% Vol. xxiii, p. 567. All Dr. Hicks's papers have instructive relative 

 coloured plates. 



§ ' Seeman's Journal of Botany,' ] 867, p. 338. 



