[VoL. 3 
500 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
RENNET 
The property possessed by the juice of certain plants of 
causing milk to coagulate was known as early as the sixteenth 
century, notably in the case of Galium verum. According to 
Green (793), this plant is still in use at the present day for 
the coagulation of milk in cheese-making. Green, Oppen- 
heimer (710), and Euler (712) have comprehensively reviewed 
the literature on the occurrence of rennet in the higher 
plants. Oppenheimer (210, p. 317) also lists certain bacteria, 
such as Bacillus amylobacter, B. mesentericus var. vulgatus, 
and B. prodigiosus, which cause the coagulation of milk. It 
has been observed by a few workers that rennet is present in 
certain fungi, especially Aspergillus and Penicillium (Oppen- 
heimer, p. 317). Buller ('06) found this enzyme to be very 
active in the juice from the sporophores of Polyporus squa- 
mosus, and Bayliss ('08) reports it for Polystictus versicolor. 
In fact, the existence of rennet in the Basidiomycetes is con- 
sidered general. Gerber (709) has demonstrated its presence 
in 86 species. Of the wood-destroying forms, he examined 
Stereum purpureum Ег., Polyporus adustus Willd., P. betu- 
linus Bull, P. hispidus Bull, P. giganteus Pers., Trametes 
Bulliardi Fr., T. gibbosa Pers., T. suaveolens L., Daedalea 
borealis Wahlb., Hydnum repandum L., Armillaria mellea 
Vahl, and Lycoperdon piriforme Schaeff. 
Our experiments show that rennet is present in both the 
mycelium and sporophores of L. saepiaria. After incubating 
at 25-30°C. for 3 hours the coagulum was formed by the 
mycelial dispersion, but it took 7 hours to form a coagulum 
in the sporophoral dispersion. There was no coagulation in 
the boiled or water control after 20 hours, the toluol keeping 
it antiseptic. The results show that the rennet is more active 
in the mycelium than in the sporophores. 
The biological importance of this enzyme in plants is en- 
tirely a mystery. There arises the supposition a priori that 
one has to do here with some peculiar phase of protease 
activity, since in animal life the activity of rennin seems to 
be closely linked with the proteases of the gastric and pan- 
creatic juices. 
