

Fig. 213. — Omphalia flavida on a leaf of Bryophyllum calycinum. Semi-diagrammatic drawings 

 (based on laboratory cultures on isolated leaves kept on wet sand), to show the development 

 of a leaf-spot (which is luminous), the production of gemmifers and of a perfect fruit-body, 

 and the dissemination of gemmae and basidiospores. A, a cross-section of part of a leaf upon 

 which a gemma has just settled after being blown from its pedicel by the wind. B, the same, 

 ten days later : from the gemma which fell on the leaf the infection hyphae grew into the leaf 

 and the mycelium of the parasite then progressively killed the host-cells there, thus forming 

 a necrotic lesion in the form of a blackish leaf-spot ; from this spot gemmifers have developed 

 and are still developing centrifugally ; the younger gemmifers have straight pedicels ; the 

 older gemmifers have pedicels which are bent basally owing to mutual repulsion and bent 

 above sigmoidally owing to a double reaction to the stimulus of gravity. The gemmae of the 

 older gemmifers have nearly horizontal axes. C, the same as B, 3-4 weeks later : the leaf -spot 

 has increased in size, but is no longer extending ; the gemmifers are all mature and two of 

 the gemmae have just been blown from their pedicels in the direction shown by the arrows ; 

 a perfect fruit-body has developed at the edge of the leaf-spot and is now discharging 

 clouds of spores which are being carried away by the wind. Drawn by A. H. R. Buller and 

 Ruth Macrae. Magnification, 6-6. 



