the Spores 0/ Varicellaria. 447 



a white corpuscle, which, towards the septum separating the 

 cells, in most spores stretched out the sporal wall on one side. 

 Thence I sometimes saw a white oblong corpuscle spon- 

 taneously expelled from either cell. When free (or partly 

 remaining within the cells and partly protruded near the sep- 

 tum), these corpuscles became larger, and especially longer, 

 than when enclosed within the spore, somewhat deformed, and 

 unequal or almost cerebriform on the surface, but covered by 

 no cellular membrane. 



Here, unless I am deceived, is the beginning of the thallus 

 of the Lichen ; but I have been unable to pursue the ulterior 

 evolution. Does, then, fecundation take place in these corpus- 

 cles ? Their analogy would then be with the spores of the 

 Fucaceae. 



Subsequently, in the warm summer, I experimented with 

 other cultivations of the spores of Varicellaria ; and, as in the 

 former ones, I beheld the mucedinous filaments speedily and 

 copiously evolved from all. But now the fructification of 

 Helminthosporium (spores septate, black, pyriform, moniliformi- 

 proliferous, subfasciculate) appeared in these filaments, and the 

 sporal wall became dissolved in a short time. Sometimes the 

 corpuscles assumed a rose-colour. Too much heat (often 

 about 30° C.) was injurious to this culture. 



Observations of this kind are very easily instituted and 

 explained ; but in such experiments the natural conditions are 

 so imperfectly imitated that consequently it is most difficult 

 to attain to any knowledge of the physiology of Lichens. 



Corrigenda. 



In Dr. Nylander's paper on " Lichens in the Luxembourg Gar- 

 dens" (Ann. & Mag. Nat. Hist. ser. 4. vol. ii. p. 245), I have inad- 

 vertently made some gross mistakes, which need correction : — 



Page 246, fine 5, for " hygrometer " read hygiometer. 



Page 248, line 31, for " Lecanora umbrina = Lec{dea pelidna, Ach.'^ 

 read: — Lecidea umhrina is identical with Lecidea pelidna, Ach., 

 which latter name is to be preferred for this lichen, because we 

 have a Lecanora umhrina (Ehrh.) and because it is desirable to avoid 

 a similarity of nomenclature in genera which approach so closely to 

 each other. 



For "Heppe" read Hepp passim. W. A. Leighton. 



