,^ NOTES AND COMMENTS. 493 



of the genus Calospora. When placed on the uninjured upper surface 

 of the leaves the ascospores germinate, the germ-tube enters the leaf 

 through a stoma, and the mycelium develops in the tissues, pro- 

 ducing a Hainsea form with amber-coloured gonidia pustules, in 

 every way resembling the original. 



We may represent the life-history in tabular form thus : — 



Calospora vanillic. 



Hainsea form 



I 



spores (gonidia) 



rudimentary mycelium 



stroma of | 



Cytispora form secondary gonidia 



I which reproduce by 



I budding, yielding a 



spore-receptacles (pycnidia) yeast - like mass. 



I Further develop- 



spores (gonidia) ment unknown. 



mycelium I 



I ^ precisely similar to previous Cytispora form 

 pycnidia ) 



perithecia of Calospora form — on dead damp leaves 

 ascospores 

 Hainsea form, similar to the original, on living leaves. 



The death of the plant is caused by the earliest or Hainsea form 

 of this pleomorphic fungus ; the two other forms appear only on the 

 dead or dying leaf. Destruction of the leaf necessarily affects the 

 whole plant, and symptoms of the disease may appear in the blacken- 

 ing tips of the " pods " before the leaf itself is visibly affected, the 

 disorganisation of its internal tissues through which the mycelium is 

 spreading preventing the proper performance of its functions and 

 seriously affecting the food-supply to all parts, and especially the 

 rapidly-developing fruits. A possible remedy, Mr. Massee suggests, 

 may be found in the fact, brought out in this examination, that the 

 Hainsea form is apparently unable to reproduce itself directly on 

 other living leaves, but is only developed from Calospora spores which 

 are themselves produced only on damp dead leaves. Hence it follows 

 that the continuance of the disease depends on the presence of 

 diseased dead leaves, and " if all fading and dead leaves are destroyed 

 by burning, the fungus pest would soon disappear, or at least be so 

 reduced as to produce no appreciable damage." It is probable that 

 impaired vitality of the plants would favour the spread of the 

 disease, as weakly specimens would almost certainly be more suscep- 

 tible to attack. This idea is supported by the fact that the disease 

 was most prevalent in flat damp places with insufficient drainage. 



It is interesting to read that since the investigation just described, 

 all the stages of the disease have been followed on cultivated orchids 

 of the genera Oncidium and Dendrobium. 



