xm] "DAMPING OFF" OF SEEDLING-TREES. 279 



that this explains how it is that the disease is spread 

 in patches from centres, and also why the spread is so 

 rapid in close, damp weather. 



When a conidium germinates in a drop of dew for 

 instance, the normal process is as follows. The proto- 

 plasm in the interior of the pear-shaped conidium 



Fig 44 —Portion of epidtrmis of a beech-seedling, on which the conidia of the 

 Fhyiofhthora have fallen and burst, a and d^ emitting the motile zoospores, b^ 

 •winch soon come to rest and germinate, r, by putting forth a minute germinil 

 hypha, c, <?, which penetrates between the cells of the epidfrm^s, e and_/, and 

 forms the mycelium m the tissues beneath At ^ a zoospore has germinated, 

 without escaping from the conidium (Highly magnified : partly after De Eary 

 and Hartig ) 



becomes divided up into about twenty or thirty little 

 rounded naked masses, each of which is capable of 

 very rapid swimming movements ; then the apex of 



