RECENT RESEARCHES INTO THE NATURE OF LICHENS. 151 



other than their gonidia. For instance, he believes that he has 

 detected grains of phycochrome in the spores of some Collemese 

 and Parmehese, and a green substance in the hyphse of the thallus 

 of Pa7inariu triptophylla. 



He regards the researches of Janczewski, of Thuret, and of 

 Bornet, which give us a knowledge of the complete life-cycle of 

 Nostoc as affording strong evidence in favour of Schwendener's 

 theory, but he does not consider that it suffices to prove the 

 autonomy of Nostoc. The well-known heteroecious mcde of 

 life of Fungi, as well as their polymorphism, render it quite 

 probable that such phenomena should also be observed in a 

 group so nearly allied to them as that of the Lichens. 



Then follows an account of various observations of compara- 

 tively small importance which tend to prove the similarity of the 

 tissues of Lichens and Fungi, and of others respecting the 

 mode of connection between the hypha and the gonidia, which 

 he has found, in some cases, to be different from that described 

 by Bornet. With reference to the development of the gonidia 

 he concludes from his observations upon Usnea barbata, Alectoria 

 iubata, and Ramalina farinacea, that in the apices of the 

 branchings of these Lichens gonidia are developed from the 

 hyphse, for he found them quite isolated in such positions that 

 their origin could not be referred either to a division of pre- 

 viously existing gonidia or to the entrance of zoospores from 

 without. He detected a peculiar mode of development in 

 Cladonia rangiferina. At the extremities of the branchings of 

 the thallus he found groups of cells, with ill-defined contours, 

 in which the hyphse became lost. Near to the apex these 

 cells are colourless, but farther back they are coloured green 

 (gonidia), and between these extremes all intermediate stages 

 occur. The author is inclined to regard these groups of cells as 

 Soredia. 



In many foliaceous and crustaceous Lichens, such as Nephro- 

 ma levigatum, Sticta pulmonacea, Ptltigera ca?iina, and others, 

 he detected another mode of development of gonidia. All thf se 

 Lichens are invested either on one or on both surfaces by a 

 cortical layer of pseudo-parenchyma. A gradual transition can 

 be made out between the colourless cells of this tissue and 

 others, lying internally, with completely green cell- contents 

 (gonidia) . 



In Pannaria triptophylla the author also detected some in- 

 structive peculiarities. He found that the tubercles on the 

 surface of the thallus at an early stage contained only one goni- 

 dium, or at most a very few, and in this condition they resemble 

 Nostoc- cells or filaments. When these tubercles are mature 

 they usually are ruptured and through the opening filaments of 



