346 
NOTES AND MEMORANDA. 
the bacteria multiplied prodigiously ; but, on the contrary, no sign of 
multiplication was observed in the other tubes. 
To make the abundant multiplication of bacteria in the nutritive 
liquid evident, I followed the same process which I employed in 1872, 
and which is described in my researches on bacteria,* a process in 
which the prodigious multiplication of the bacteria was revealed by 
the turbidity and characteristic cloudiness of the nutritive liquid 
which at the commencement was colourless and transparent. | 
Development of Lichens . — The second part of Stahl’s ‘ Contribution 
to the Development-History of Lichens ’ has been published. It treats 
of the nature of the hymeneal gonidia. We find in the hymenium of 
Dermatocarpon Schoereri, crossing freely between the thecae, globular 
gonidia which diifer from those of the thallus by their still smaller 
size, and which are expelled from the perithecium at the same time as 
the ripe spores. When this simultaneous emission is made on a 
suitable substance, the spores germinate, and the tubes arising from 
their germination surround the hymeneal gonidia, which soon attain 
the dimensions of those of the thallus. We may then see in a short 
time the reproduction of Dermatocarpon Schoereri furnished with its 
characteristic thallus. 
The baculiform hymeneal gonidia of the Pohjhlastia rugulosa, which 
agree in their characters with the free Algae of the genus SticJiococcus^ 
have furnished the observer with phenomena identical with those of 
Dermatocarpon. A little species of Thelidium, not yet described, very 
often accompanies Dermatocarpon, and the gonidia of these lichens are 
specifically identical. If a cultivation experiment is so arranged as to 
bring the spores of the Thelidlum into contact with the hymeneal 
gonidia of Dermatocarpon perfectly free of all mixture, we obtain, as 
the result of the experiment, the thallus of the Thelidium with its 
characteristic fructification. The same Alga which gives these gonidia, 
and which is, according to the author, a sj^ecies of Protococcus, may 
consequently bring itself into relation with two ditferent Ascomycetes, 
in order to form two lichens also ditferent. J 
3Iicroscopical Study of the Ashes of Leaves . — At the Indianapolis 
Congress Dr. R. H. Ward, of Troy, described the method by which 
leaf ashes may be prepared so as to preserve much of the structure of 
the leaf. 
The books speak of the siliceous residue of the leaves of the 
grasses, but many other leaves are equally available ; leaves of trees 
are generally used with more success than those of herbs, and they 
should be gathered late in the summer. 
A piece of dry leaf is laid on a strip of platinum foil or thin mica, 
covered with mica or a cover-glass to prevent curling up, and carefully 
heated over an alcohol lamp or Bunsen burner until the organic 
matter is slowly burned out, and the mineral matter, or ash, remains 
* ‘ Beitrage zur Biologie d. Pflanzeii,’ by Professor F. Cohn, pp. 218 and 196. 
1872. 
t M. A. Howath, in ‘ Comptes Rendus,’ vol. Ixxxvi. p. 703. — See, for further 
details, my work presented to the Biological Society, January, 1878. 
X ‘ Bull, de la Soc. Bot. de France,’ vol. xxv. p. 32. 
