CITRUS DISEASES. 



87 



ing on them as on the fruit. Wliere infection is not general, very 



ijuirked conical pro- 



Fig. 1.3. — Citrus scab on lemcn leaves. 



Fig. 14. — Character- 

 istic conical pro- 

 jection caused hy 

 citrus scab on 

 grapefruit leaf. 



t ration in e i t h e ^ 

 leaves or fruit of the 

 inner host tissues. In 

 fact so effectively are 

 - the inner tissues pro- 



tected that scabbed fruits are no more subject to decay than nor- 

 mal ones. 



Cause. 



The disease is produced by the action of a parasitic organism. 

 This spreads from place to place by means of exceedingly minute 

 spores or spore-like bodies. Many workers have confused, in this 

 connection, certain fungi with the casual organism, so that further 

 work is necessary to properly place and name l)otanically the latt(M-. 



It is quite connuon to find one or more fungi in and about scab 

 areas which are, however, merely secondary. The scab organism is 

 not visible at any time to the unaided eye, either as a black mold 

 or otherwise. 



