ccxvi GENERAL SUMMARY OF SCIENTIFIC AND 



however, seems to be the fact. The lichenologists, as the 

 term is generally applied, look at the question from one side 

 only. Their object is to describe and arrange large numbers 

 of species, not to follow out the details of the development 

 of any one. In classifying their species, the professional lich- 

 enologists have made use principally of the fruit, and paid 

 but little attention to the gonidia. It is the presence of go- 

 nidia which, even according to the lichenologists, is charac- 

 teristic of the lichen rather than the fruit, which is, as is ad- 

 mitted by every one, precisely similar to that of the ascomy- 

 cetous fungi. The structure of the gonidia and their devel- 

 opment has been vastly better made out by Schwendener 

 and Bornet than by any of the lichenologists proper, who, in- 

 stead of giving good figures and accurate descriptions of the 

 growth of the gonidia from the hyphse, which they maintain 

 takes place, are satisfied with the mere statement that some 

 one or other, not noted for his skill at the microscope, has 

 seen, or thinks he has seen, this growth. If such an organic 

 union between the hyphre and gonidia exists, certainly skillful 

 microscopists, whether lichenologists or not, ought to be able 

 to see it. But such is not the case. If the Schwendener 

 theory is not tenable, the only feasible theory is that of Pro- 

 fessor Theodore Fries, who believes lichens are bodies con- 

 sisting of hyphae, or threads, and gonidia, and that the latter 

 can exist without the former, and when found free have been 

 erroneously considered algse by some botanists; that is to 

 say, the Oscillariea?, the Palmellese, and other groups of algge, 

 are not really alga? at all, but gonidia of some lichen which 

 have escaped and are living free. This view might be con- 

 sidered the true one were the gonidia of lichens limited to 

 such forms as Oscillaria, Rivularia, and Palmella, whose 

 method of reproduction differs somewhat from that of plants 

 which are universally recognized as algse. But in the genus 

 Opegrapha the gonidia correspond in appearance to a genus 

 of alga3 known as Chroolepus, and M. Bornet has shown that 

 they are propagated in the same way. Now Chroolepus is 

 nearly related to Cladophora, and many other genera of un- 

 doubted alga?; and if we suppose that Chroolepus is nothing 

 but an escaped form of lichen-gonidia, we must make the 

 same supposition with regard to Cladophora, Chaitomorpha, 

 and other genera which live in both salt and fresh water, 



