492 



NATURAL SCIENCE. 



by a microscopic fungus which Mr. Massee calls Calospoya vanUlo'. 

 In the Kew Bulletin for May and June last he gives an account of his 

 examination and the results obtained. The latter are also interesting 

 from a purely scientific point of view in elucidating the life-history of 

 a fungus, only one stage of which was previously known. The study 

 of the life-history also suggests a remedy as far as this can be possible 

 without a thorough investigation of all the circumstances conducted 

 on the spot. 



Living leaves attacked by the disease show minute amber- 

 coloured pustules springing in small groups from slightly discoloured 

 patches, which are most abundant on the upper leaf-surface. These 

 pustules consist of masses of spores or gonidia, evidently belonging 

 to the genus Hainsea, borne on a mycelium which is rapidly destroy- 

 ing the leaf-tissue ; the fungus proves to be identical with the 

 Glceospovium vanilla received in 1886 on specimens of the same 

 species of Vanilla from Antigua, and described by Messrs. Cooke and 

 Massee, who did not recognise the connection between the several forms, 

 though all were present. These gonidia germinated when sown in a 

 nutrient solution producing a mycelium and secondary gonidia ; the 

 latter when sown reproduced enormously by budding, yielding a 

 mass of yeast-like cells, but were never seen to emit a germ-tube. 

 No result was obtained when living Vanilla leaves were infected with 

 them, and it is unknown to what they eventually give rise. When 

 the Hainsea fungus is fully developed the leaf has become yellow as 

 the result of its ravages, and is evidently dying. At this stage very 

 minute clusters of black points can be seen beneath the cuticle. 

 These on examination were recognised as black-walled spore- 

 receptacles or pycnidia belonging to the form-genus Cytispova. 



The pycnidia were partly sunk in a common cushion or stroma 

 formed from a mycelium quite indistinguishable from that of the 

 Hainsea, which preceded it. Their gonidia ooze out through the 

 ruptured cuticle like "mucilaginous tendrils" forming pale yellow 

 waxy masses on the leaf-surface. When allowed to germinate on 

 the moist epidermis of an uninjured Vanilla leaf they did not enter the 

 leaf, the germ-tube being apparently unable either to pierce the 

 epidermis or get in by the stomata ; but when placed on a dying leaf 

 after commencement of disintegration they penetrated and spread 

 through it, producing pycnidia in abundance. This shows that 

 the Cytispova is a saprophyte and will not reproduce itself on the 

 uninjured living leaf. B}' the time the Cytispoya has completed its 

 development the leaf has become dry and shrivelled, the whole of 

 the sap and protoplasm having disappeared. No further develop- 

 ment occurs as long as it remains dry, but if kept damp the stromata 

 produce perithecia from the central portion. Though their develop- 

 ment was carefully watched, no trace of an ascogonium or " Woronin's 

 hypha " was seen indicative of a sexual process. The perithecia 

 contain asa, each with eight ascospores, and exactly resemble those 



