34 PROGRESS OF MICROSCOPICAL SCIENCE, 



they arc divided into two, four, or eight masses, separated by a dis- 

 tinct i)artitioii, but still enclosed in the hyaline cell wall. It must be 

 remembered that each of these granular brownish-black bodies is a 

 separate plant, and it is only by their rapid increase and aggregation 

 into masses that the patch we see on the tree is produced. It is a 

 matter of considerable difficulty to convey in writing a clear descrip- 

 tion of these minute forms of life; but I trust, by the help of the 

 specimens and drawings on the table, I have made sufficiently clear 

 all the data we have to enable us to find out its position in the vege- 

 table kingdom. I may, however, mention that no reaction is found on 

 the contents of the perithecium either by potash or iodine. 



The question first arises, after having ascertained its structure. 

 Where are we to look for it? The general appearance is certainly 

 that of a Lichen, and the black oblong or ovoid perithecia have much 

 the appearance of some of the Graphidcfe. The spores and asci give 

 us no help, as they may belong either to a Lichen or a Fungus. The 

 great difficulty arises from the presence of the green particles, temied 

 gonidia, which are identical with some of the Algse, and have been 

 figiu'ed and described under various names by Kiitzing, Hassal, and 

 others, as separate and distinct plants ; but similar bodies are also 

 found in Lichens ; and we find the Eev. M. J. Berkeley, one of our 

 greatest authorities, in his introduction to Cryptogamic Botany, 

 defines Fungi as " plants Hysteroj)hytal (that is, living upon dead or 

 living organic matter) or Epiphytal (that is, growing upon another 

 plant), noui'ished by the matrix, nevei' producing gonidia ; " whilst his 

 definition of Lichens is "Aerial, nourished by air, and not by the 

 matrix, producing gonidia," Of course, with these definitions, anyone 

 would naturally expect to find our plant amongst Lichens ; but a most 

 carefid examination of Leighton's ' Lichen Flora,' the latest and best 

 work on this tribe, together with Mudd's Manual and other works, 

 failed to show me any description that would agree in all respects with 

 the appearance shown by the plant I have described. I then asked 

 Mr. Muller to examine it, and ascertain if it could be a Fungus. The 

 mixture of distinguishing characters was as gi'cat a puzzle to him as 

 it had been to me, and he was unable to make out from Cooke's Hand- 

 book its exact position ; but on carefully going through the ascomy- 

 cetes Fungi in Hooker's ' English Flora,' he found Hysterium rugosum 

 described as "Stroma, crust-like, innate, brown-black, perithecia elliptic 

 bursting through the living bark, at length running together into irre- 

 gular spots." This is said to be extremely common on the smooth 

 branches of birch and oak. And Mr. Berkeley, who prepared this 

 portion of the British Flora, states also that it is usually referred to 

 the order Lichenes, from which, however, Messrs. Borrer and Hooker, 

 in accordance with the views of Chevalier, Wallroth, and Fries, con- 

 sider it extraneous. Sir James Smith long since perceived its affinity 

 with Hysterium, from which it differs in the presence of a stroma, and 

 in its being j)roduced on living bark. Reference is made to ' English 

 Botany,' t. 2282, and on looking at the figure and description there 

 given, as well as to the works of Fries, Acharius, and other authors, it 

 was evident this was undoubtedly the plant we were in search of. The 



