Y, ORIGIN OF MOULD. 208 
appears in a horizontal pofition, it foon rifes per- 
pendicularly, and fo continues to grow. It is 
otherwife with mould. I have often cut a piece 
of melon, gourd, or bread, into a cube: mould 
vegetated on the four lateral furfaces, and the 
ftalks had conftantly every other than a perpen- 
dicular direction (1). 
The other property, which was difcovered by 
the celebrated Genevefe naturalift, is the ten- 
dency of plants to turn towards the light. In 
addition to the facts he recites, which are fufhi- 
cient to afcertain the property, I have frequently 
obferved it in legumes growing in infufions, fhut 
up ina prefs: the plants always bent towards a 
chink that admitted a flender ray of light; and if 
this chink was {topped up, and a new one open- 
ed in a different part of the prefs, the plants a- 
bandoned their original direction for this new 
one. I could never difcover that light had the 
leaft influence on mould. ; 
If ripe mould is fhaken, a kind of black duft 
falls from it, which the celebrated botanift Mi- 
cheli has fuppofed the feed of the plantula; but 
the 
(1) This may generally happen; but I have, in many 
imftances, feen an evident tendency to perpendicularity, 
and vegetation in a ftraight line. Deviation from it may 
perhaps be chiefly occafioned by the extreme delicacy of 
the ftalk.—T, 3 
