THE PRINCIPLES OP BOTANY. 
545 
quently contracted the malady, but it has rarely happened 
that its cure has proved intractable. The same phenomena 
have been observed again and again among herdsmen who 
had to attend to affected cattle. The circumstance noted by 
Mr. Nettleship of the disease being absent from Dutch calves 
most likely is to be explained by their being fat calves, as such 
only are now imported into England. Eat calves are as a 
rule free from ringworm, which, doubtless, depends to a con- 
siderable extent on their living on milk, and the general clean- 
liness which is observed towards them. Weaned calves, on the 
contrary, as might be expected from their being differently 
lodged and provided for, are highly suscptible to ringworm. 
The age of the animal should also be borne in mind when we 
endeavour to explain its seeming immunity from the disease. 
Eat calves rarely exceed twelve or fourteen weeks of age 
when slaughtered, and it is not until after this time that we 
see many cases of ringworm among animals in general. — 
Eds.] . 
THE PRINCIPLES OF BOTANY. 
By Professor James Buckman, F.L.S., E.G.S., &c. 
( Continued from p. 444.) 
The last alliance of the Thallogens which we have to ex- 
amine will be the Lichenales, known as Lichens and Liver- 
worts. These curiously illustrate the fact that scarcely an 
atom of the earth’s crust, or indeed of the superficies of any- 
thing placed thereupon, but may become the nidi of some 
species of Lichen. Thus the variegated colours of rocks, 
stones, and buildings ; tbe black, grey, yellow, and brown 
blotches on the boles of every tree ; and the crustiform 
beards on the surface of the moor, on old palings, and fring- 
ing the branches of oak, apple, and other trees, are but so 
many forms of Lichens. Henfrey says, “ The spores of 
Lichens are produced in the cavities of special parent-cells, 
which are called thecae or sporangia. These are accompanied 
by a number of filiform cells ( paraphyses ) resembling those 
occurring with the sporangia of the Fuci, &c., and are collected 
together in groups of a definite form on the upper surface of 
the thallus, generally more or less immersed in its substance. 
The young thecae contain a variable number of spores, 
usually eight to twelve, but seldom perfect more than one 
or two.” ( 4 Structural and Physiological Botany,’ p. 115.) 
