[Vor. 1 
294 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
Behrens (6) investigated some of the physiological relations 
of saprophytes in comparison with parasites, using Mucor sto- 
lonifer, Penicillium sp., Botrytis cinerea, and Oidium ( — Sclero- 
tinia!) fructigenum. This author holds that Sclerotinia does 
not produce a cellulose-dissolving enzyme, and that the fungus 
merely forces its way through the host tissue by a purely me- 
chanieal force, or that, in some cases, it splits the middle lamella 
but does not dissolve it. In the case of the other fungi mentioned 
above he believes that an enzyme is secreted which dissolves 
the middle lamella. The cause of the injury due to Sclerotinia, 
he holds, is not that the cellulose walls or the pectin of the 
middle lamella is dissolved, but that the turgor and the osmotic 
relations of the penetrated cells are materially modified. Ac- 
cording to this author some substance diffuses through the 
walls and stimulates the fungus to bore through or between the 
сей walls. He demonstrated in Botrytis and Penicillium, more- 
over, a thermo-stable toxic body which disintegrated the host 
cells, and believes that these fungi secrete a pectin-dissolving 
enzyme which is different from that which acts upon cellulose. 
Nordhausen (40), at about the same time, made similar studies 
on Botrytis cinerea and comes to similar conclusions. He finds 
that the enzyme does not cause a strong swelling of either the 
Idle lamella or the cellulose cell walls, the action in this respect 
g more like that of de Bary's Леска. Smith (46) stud- 
Ве parasitism of Botrytis cinerea, but in certain particulars 
dot get the same results as de Вагу and Ward. Like them 
e finds that the parasite secretes some soluble substance that 
penetrates and kills the living cells in advance of the fungous 
filaments, but unlike Ward he could detect no swelling of the 
cell wall. Smith believes that this toxic substance is not an 
мы enzyme, for boiling does not inactivate it, but thinks that it is 
perhaps oxalie acid, since this substance is always present in the 
cultures and amounts in some cases to as much as two per cent. 
The analytieal methods whereby the oxalie acid was determined, 
unfortunately, are not given. 
Schellenberg (43) investigated the action of several sapro- 
phytic and parasitic fungi on hemicelluloses from a number of 
! Wehmer, C. Ber. d. deut. bot. Ges. 16: 298-307. 1898; Saccardo, Syll. Fung. 
4: 34. 1886. 
