1877.] : Botany. 365 
this result; but if the wood is artificially charged with water, no air can 
be forced through it. 
Another portion of the paper refers to the resistance which the walls of 
wood cells offer to filtration. If distilled water and fresh wood be used, 
filtration can be conducted with great rapidity. The rate diminishes 
after a very short time. Professor Sachs has also examined the amount 
of air in cell-cavities. This amount he has endeavored to determine 
by a series of calculations, and he gives the following results : — 
Fir-stem, 100 cubic centimeters 25 ce. of cell-wall, 58.6 ce. water (in 
the cell cavities and imbibed by the walls), 16.4 cc. air-space. Geleznow 
had obtained different results, namely: 100 cc. fresh Betula alba wood 
contain 32.4 ec. cell-wall, 33.2 cc. water, 34.4 cc. air-space. 
It may be said in conclusion that Professor Sachs has found reason 
for emphasizing the statement in his text-book that a distinction must be 
made between the passage of water through wood by means of capillar- 
ity acting in the capillary cells, and by adhesion to the cell wall. The 
communication will lead botanists to look with interest for the memoir 
of which the present short paper is only a forerunner. 
Onton Smurt.1— Dr. Farlow’s essay on this subject is of great value 
as well to the agriculturist as to botanical science. 
The smut plant ( Urocystis Cepule) makes its appearance upon t 
onion leaves while they are still quite young. often changing the ania 
portion iuto a mass of black, dusty spores, previous to the formation 
of which the threads of the fungus have penetrated like a network 
among the cells of the leaf tissue. 
It is peculiar to America, and has probably come from some of our 
Wild species of onion. As a means of checking its ravages, which are 
Row limited to only a few localities, the author suggests as a wise 
precaution, the destruction of all wild and useless species of onion. 
Ground on which the smut has appeared should be burned over, and 
the earlier in the season the better. A knowledge of allied species, sup- 
ported by a limited experience of the disease in hand, tends to show - 
that the smut spores do not retain their vitality for more than four 
years; therefore by growing some other crop for a few seasons a partial 
eradication at least might be expec 
It remains for the suffering onion, growers to profit by this excellent 
instruction, and do all in their power to prevent the spread of the dis- 
ease into new localities 
With the aid of the plate, in which are figured the plant under con- 
sideration, rye smut, and spores of the corn smut, the relations which 
the onion smut bears tp some of the other members of the order Usti- 
ginee are pointed out. In a note at the close of the paper the new 
fungus is botanically described. — B. D. H. 
1 Onion : nted by Dr. W. G. Farrow, of Harvard University, 
to the anor Bocleey ir rostit Agriculture, and published with a plate 
in their Twenty-fourth Annual Report 
