500 SUMMARY OF CURRENT RESEARCHES RELATING TO 



arc simply portions of the ordinary byphic, Avliicli increase in length 

 by apical growth, while the ascogonial cells increase at the same 

 time in size by intercalary growth. The cortical fibres and the 

 ascogonial tissue are strongly differentiated from the first. The next 

 period of development commences Avith the formation of the first para- 

 physcs, commencing in the cortical layer of tltc apothecium. A mass 

 of yoiing cortical fibres in the middle of this layer displays delicate 

 shoots which develope into the paraphyses. These gradually extend 

 over the entire cortical layer of the aiiothecium, new ones being 

 formed between the older ones. At the same time the separate asco- 

 gonial cells shoot out and form the ascogenous hyphal tissue. Tlic 

 process of disorganization of the ascogonia runs parallel with the 

 formation of this tissue, and finally the asci are formed as bulgings 

 of the ascogenous hypha; ; the outer part of the cortical layer bursts, 

 and thus is formed the " excipuliun thallodcs " of lichenologists. 

 The formation of the apothecium is not the result of any sexual pro- 

 cess, the strong differentiation of the ascogenous hyphno from those 

 which develope into paraphyses being traced back to the youngest 

 stage. The author regards the process as the same as that in Podo- 

 $2)]ia'ra among Ascomycetes, apogamy with rudimentary sexual organs. 



The processes are nearly the same in Peltidea aphtJwsa and 

 venosa, while in Nepliroma tomcntosum and Ictvhjatum there arc im- 

 jiortaut deviations. In these species the author always found spermo- 

 gonia, though always in a rudimentary condition. The first apothecial 

 layer is formed beneath a thick close cortical layer on the margin of 

 the thallus by a number of large thin-walled cells arranged in a 

 moniliform manner, and from the analogy of Peltujera and Peltidea, 

 regarded as ascogonia, developed gradually from ordinary hyphge of 

 the thallus. The entire structure is enveloped in a dense hyphal 

 tissue, which gradually disappears as the fructification developes ; 

 and the apothecia of Nephroma are hence described as gymnocarpous. 

 The formation of the ascogonia was not clearly observed. The 

 mode of formation of the paraphyses is similar to that in PeJti- 

 f/era, but takes jjlace later. The paraphyses anil asci are always 

 formed on the under side of the thallus, so that the young aj)othecia 

 at first face the substratum ; their position is subsequently reversed 

 by a strong curving of the fertile layer. 



We have therefore in these lichens similar phenomena of apogamy, 

 and the reduction of sexual organs, to those that have been observed 

 in the Ascomycetes. 



Nature of Lichens.* — Prof. M.M. Hartog replies to Rev. J. M. 

 Crombie's paper | on the " Algo-lichen hypothesis." He points out 

 that Mr. Crombie altogether ignores several points Avhich tell strongly 

 in favour of Schwendcuer's hypothesis, especially Cora and Johow's 

 discoAx^ry of the Hymenolichenes, or lichens in which the fungal element 

 is a Hymcnomycete. He also states that the " lichcnin-reaction " has 

 been observed by De Bary in several undoubted Fungi, and contests 

 Mr. Crombie's statement that fungus-hyi)li{e are soluble in caustic 

 jjotash. 



* Nature, xxsi, (18?5) pp. 376-7. t Sec this Journal, ante, p. 103. 



