6l2 
Journal of Agricultural Research 
Vol. XXI, No. 9 
secreted an enzym—pectinase—which has no action upon lignified or 
cuticularized walls, but which has the power to dissolve the middle 
lamella considerably in advance of the invasion of the bacteria. 
Spauding (15) observed that in the last stages of decay produced by 
Lenzites sepiaria Fr. the middle lamellae have disappeared. Zeller (19) 
found that the same wood-destroying fungus produced a substance called 
pectinase capable of dissolving the middle lamella of carrots and potato 
disks, coherence of the tissue being entirely lost after 42 hours in an 
extract of the fungus powder. 
Probably the most important contributions to the physiology of para¬ 
sitism, at least as regards the intimate relations of the host to the parasite 
concerned, are those of Brown (4, 5), Dey ( 6 ), and Blackman and Wels- 
ford (3). 
It was shown that Botrytis cinerea Pers. acts in advance of its growth 
and that the active principle is of the nature of an enzym which dissolves 
certain constituents of the cell walls. It was further shown that the 
death of the protoplasmic contents of the cells was subsequent to the 
maceration of the plant tissues. To what the death of the cell is due 
appears to be a controverted point. Brown has been unable so far to 
identify two distinct principles in extracts of Botrytis mycelium. On 
the other hand, DeBary’s (1), Nordhausen’s (12), and Behrens’ (2) con¬ 
clusions seem to argue in favor of the presence of both an enzymic and 
toxic principle. Brown (4) showed that there was 110 dissolution of the 
underlying host tissues when extracts of the mycelium were placed on the 
unwounded surface of the host, and Blackman and Welsford (3) showed 
that the penetration through the unbroken surface of the host was ac¬ 
complished by mechanical pressure. Similar results were obtained by Dey 
(< 5 ) with Colletotrichum lindemuthianwn (Sasc. and Magn.) Bri. and Cav. 
A resume of the literature shows that various investigators have drawn 
quite different comclusions from the results of their experiments. Per¬ 
haps criticism of some of the earlier investigations might be justified on 
the grounds that they failed to describe their methods in sufficient detail 
to enable the reader to evaluate their results correctly. Furthermore, 
some of the conclusions have been drawn from the results obtained by the 
use of extracts of mycelium grown for a long time in culture, in some cases 
three weeks or more. It is probable that the material used had lost much 
of its power to dissolve the middle lamella, since Brown (4) showed that 
the macerating principle was most active in young and vigorously grow¬ 
ing hyphae of Botrytis cinerea 1 to 2 days old. The writers also have 
found that the intracellular pectinase of Rhizopus is greatest in young 
mycelium. Harter (9), Dox (7), Young ( 18 ), and others showed that 
diastase, inulase, and other enzyms were more abundant in the hyphae 
just preceding the fruiting stage. It would, therefore, seem that young 
cultures should be employed if the maximum efficiency is to be obtained 
from the use of the hyphae. 
