562 BOTANY. 
pollen from one flower must almost necessarily fall on the stigma 
of another flower. In the wheat each separate flower remains 
open only for an extremely short time, the glumes separate from 
one another suddenly, the anthers immediately protruding, and a 
large quantity of the pollen is dispersed into the air, the whole 
process not occupying more than half a minute. In most of these 
cases the stigma remains receptive only for a very short period and 
then dies, while in others the stigma remains in a receptive condi- 
tion till long after the anthers have dropped off, and then must nec- 
essarily be open to the access of foreign pollen. In comparatively 
few cases the natural contrivances appear to favor self- rather than 
cross-fertilization. Thus in the oat and barley the majority of 
the flowers never open, and are, therefore, necessarily self-fertil- 
ized; there appear, however, in almost all cases to be a small 
number of flowers, often arranged in one or two separate rows, 
which do open, and therefore may introduce occasional cross-fertil- 
ization. It is probable that the same species behaves differently 
in relation to its arrangements for fertilization under different 
circumstances of climate, while species very nearly related exhibit 
phenomena which offer a marked contrast.—A. W 
STRUCTURE AND PropaGaTion or Licuens. — The theory of 
Schwendener that Lichens are not separate organisms but are com- 
posed of Fungi, parasitic on Algse (the so-called gonidia), has not, 
up to the present time, found much favor with cryptogamic bota- 
nists, Sachs being almost the only physiologist of repute who 
has as yet adopted it. The theory has, however, recently met 
ith some countenance from the researches of Woronon on the 
lichens Parmelia pulverulenta and parietina. He confirms the pre- 
vious statements of Famintzin and Baranetzky that the gonidia 
of these lichens produce zoospores which he describes as bi-cili- 
ated ; and he gives an exact account of their mode of escape from 
the gonidia. These zoospores, after the cessation of their vibratile 
motion, caused by the cilia, become covered by a membrane after 
the ordinary mode of the zoospores of Algze, and form themselves 
into gonidiform bodies, increasing by division, but producing 
neither filaments nor hyphx, but only giving birth to new gonidia, 
in other words, to young individuals of a unicellular alga of the 
genus Cystococcus. The observation of the actual germination 
of the zoospores is a link in the chain, hitherto wanting.—A. 
