PROGRESS OF MICROSGOPICAL SCIENCE. 209 
others remain thin and transparent, and during the time the spores 
are ripening the latter are converted into mucilage, the simple or 
branched thickened segments remaining. The origin of the basidia 
is as follows: Immediately after the development of the hymenial 
masses, some of the filaments of which they are composed bear 
branches which direct themselves towards the centre of the mass; 
these branches divide transversely, and the terminal cell becomes 
elongated and is soon seen to carry four round pedicellate spores, the 
nucleus of the basidium disappearing before the spores make their 
appearance, as Woronine has already observed in Exobasidium. 
M. Sorokine cannot share the opinion of Berkeley and Tulasne that 
the spores do not arrive at their full development while attached to 
the basidia, but that they fall off and draw elements of nutrition 
from the nidus in which, when free, they find themselves. On the 
contrary, he thinks that the spores do not fall until their development 
is complete. He believes also that, contrary to what has already been 
held, there is no regularity in the order of local maturation of the 
hymenial masses. ‘I'he so-called “nucleus” of the spores is shown to 
be of oleaginous nature, since it dissolves in alcohol. 
Haperimental Observations on Mosses.—Some experiments of a very 
interesting nature were conducted lately at Strasburg in regard to the 
“artificial production of a protonema on the sporogonium of Mosses,” 
by Professor Dr. Stahl. They are described at some length in the 
‘Journal of Botany’ for January, by a writer who signs himself 
G. R. M. M. He says, among other things, that as Brefeld’s views on 
the alternation of generations of the Ascomycetes take the relations 
existing in Vascular Cryptogams as a point of departure, it was first 
of all the question whether the production of the sexual generation 
was necessarily bound up with the formation of spores, or whether 
perhaps, under normal conditions, other parts of the spore-bearing 
plant were not in a position to produce the sexual plant. To settle 
this question by experiment no better object could be found than the 
sporogonium of Mosses, and after much searching Dr. Stahl found — 
that of Ceratodon purpureus to be the most suitable for conducting 
the necessary investigations. The experiments were instituted thus. 
The sporogonia were partly extracted from their mother-plants—a 
process which can usually be effected without injury—and partly cut 
off directly above the point of their connection; all were placed on 
damp earth under a bell-jar, and exposed to diffused daylight. Nota 
few soon showed clear signs of decay; others again remained green 
and unaltered in shape, with the exception of some deformations of 
the capsule. After two or three months, however, dense protonema- 
formations, on which leaf-bearing Moss-plants were already formed, 
proceeding from the cut surface of the seta, extended over the earthy 
substratum. From microscopic examination it appeared that the 
protonema-threads owed their origin to the chlorophyll-containing 
cells within the seta, longitudinal sections of which showed the way 
they arise. After a lapse of three months the contents of most of the 
seta-cells had died in both the forms of cultivation, but here and 
there were found, extending along the whole length of the seta, 
