312 NOTES AND MEMORANDA. 



of fungi parasitic upou Algte, although not generally accepted by 

 lichenologists, has met with great favour from physiologists. Dr. A. 

 Minks promises an important work in opposition to this theory, 

 founded on a long series of experiments, and to be illustrated by a 

 large number of coloured plates. In the meantime he gives a state- 

 ment of his conclusions, with some of the arguments on which they 

 are founded, in ' Flora.' * His observations were made mainly on a 

 gelatinous lichen, Leptogium myochroum, Ehrh., and with a Hart- 

 uack's objective with a power of 1250. All the preparations were 

 made in filtered river-water, to which was usually added a larger or 

 smaller quantity of potash (" liquor kali caustici " of the German phar- 

 macopceia, Sd^ per cent.). In order to remove the jelly, the prepara- 

 tion was further heated with potash for ten minutes, every trace of 

 the alkali washed away, and dilute sulphuric acid gradually added 

 to the water in which the preparation lay. While the destructive in- 

 fluence of the acid on the true constituents of the lichen is very slow, 

 it has a remarkable effect on the contents of the cells, changing the 

 blue-green of the gonidia at once into a more or less intense steel-blue. 

 A close observation of the thallus of the lichen in question shows, 

 says Dr. Minks, that there is no clear distinction between the cells 

 of the hyphae and the gonidia, one passing over insensibly into the 

 other, the two being contrasted simply as different modifications of 

 the same cell. The cloudy granular contents of the gonidia appear, 

 when very highly magnified, as a colourless protoplasm permeated 

 by a smaller or larger quantity of intensely blue-green corpuscles. 

 The colourless contents of the hyphal cells also consist of a pro- 

 toplasm, but in their axis is a single row of similar but more delicate 

 blue-green corpuscles. The presence of these corpuscles, termed by 

 Korben microgonidia, serve to distinguish the cells of lichens from those 

 of fungi, and are the origin of all intracellular new-formation of cells. 

 The microgonidia may be considered as the germ of the new-forma- 

 tion of gonidial chains. A row of microgonidia, increasing by the 

 division of its separate corpuscles, increases the size of the cell which 

 encloses it to its utmost capacity ; this mother-cell ultimately becomes 

 dissolved into jelly, and the young chain of gonidial cells is thus set 

 free. The microgonidia gradually grow and finally become invested 

 each in its own cell-wall, beboming thus transformed into ordinary 

 gonidia. In this way an ordinary hypha of the thallus may become 

 transformed into a chain of gonidia. The gonidial cells soon lose all 

 indication of their origin, and increase by the ordinary repeated 

 bipartition or quadripartition. Some cells, however, take no part in 

 this multiplication, remaining unchanged in the form of what are 

 known as heterocysts or metrogonidia, which also contain microgonidia, 

 like the ordinary cells. The two differentiated products from the 

 same original fundamental tissue — ordinarily called the gonidial 

 system and the hyphal system — our author proposes to term gonidema 

 and gono-hyphema, the latter always having a potentiality to pass 

 over, at some time or other, into the former. In addition to these, 

 the lichen-thallus contains a third tissue, hitherto neglected, the 

 * 'Flora," xxxvi. (1872) 209 ct seq. 



