ARCHER — ON " PALMOGLCEAn" ALGJE. 273 



produce them an analogy similar to that of the buds, bulbils, &c, 

 of higher plants to their seeds. As to the so-called " Asteridia" 

 (Thwaites), " Asteroplueria," " Spermatosphceria" (Itzigsohn), &c, 

 they are most probably parasitic growths, and their true nature is as yet 

 not at all understood. 



But Dr. Hicks intends his queries, first applied to Palmogloea, to be 

 extended to certain true Palmellacean forms ; and, if applied to some 

 of the lower forms of which, I am free to own that they cannot be so 

 easily answered, nor can his objections be so readily met. 



There is a point, however, which seems to be overlooked by Dr. 

 Hicks, and a consequent confounding of two apparently essentially dis- 

 tinct groups fallen into. Dr. Hicks seems to ignore the Family Chroo- 

 coccacese as distinguished from Palmellacese ; thus, forms appertaining 

 to Chroococcaceae are sometimes, as it appears to me, indiscriminately 

 spoken of as originating from some higher plant, whose endochrome is 

 chlorophyll, and vice versa as regards Palmellaceoe. Now, in so far as 

 we know, it seems a matter not at all to be expected that such a trans- 

 formation should take place ; that is, I should be disposed to hold it 

 exceedingly unlikely that a Chlorphyll-bearing lichen or moss should 

 produce a phycocrome-bearing Glceocapsa, and that too along with a 

 chlorophyll-bearing Palmogloea. Thus Glceocapsa polydermatica surely 

 belongs to Chroococcacese, and could not be regarded as proceeding 

 from a chlorophyll-bearing lichen. A Glceocapsa may possibly origi- 

 nate from a phycochrome-bearing lichen — for instance, a Collcma ; and 

 I venture to think that in many cases where Dr. Hicks speaks of Pal- 

 mellacege, he means to refer to Chroococcaceee. Many of the forms in- 

 cluded amongst the latter, I am myself greatly disposed to think, show 

 a considerable amount of instability, and may probably be but transi- 

 tory or developmental stages of higher plants. But then they must, I 

 think, at least owe their origin to phycochrome-containing plants — some, 

 for instance, may be early stages of Scy tonemeoe. On the other hand, many 

 of the forms seem to be very recognisable, and are frequently met with, 

 season after season, precisely like their predecessors, and under the 

 same circumstances ; and one can often at a glance tell that a certain 

 form under observation is exactly the same thing that one has seen be- 

 fore. But this would not in itself be an argument that they may not 

 be, so to speak, if the phrase be at all admissible, " alternations of ge- 

 neration" of certain Lichens or Scytonemeae. In regard to Palmella- 

 ceoe, such genera as Pleurococcus, Glceocystis, and Palmella, if they are 

 all actually but developmental stages of higher forms, could at least 

 originate only from Chlorophyll-bearing plants. 



But, further, on the other hand, many of the Palmellacean genera 

 produce a very definite structure, even what may be called a frond, 

 and sometimes very definite forms of the individual cells themselves. 

 So readily do these specialities strike the eye when once they have been 

 seen, that on their recurrence they are at once recognisable. The ge- 

 neric names Apiocystis, Sehizochlamys, Palmodactvlon, Tetraspora, 



2p 



