TILLETIA TRITICI 



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pair of primary conidia, instead of producing a secondary conidium 

 as in (4), sends out a slender gerin-tube which, if nutriment is 

 available, may develop into an extensive mycelium producing 

 numerous secondary conidia (Fig. Ill, D). The falling away of the 



Fig. 112. — Tilletia tritici. Germination of a primary conidium (the authors' 

 primary sterigma) when sown by itself. A, a chlamydospore a has produced 

 a promycelium (basidium-body) b which in turn has produced twelve primary 

 conidia c ; the conidia are full-grown but have not yet conjugated in pairs. 

 B-D, primary conidia which have been isolated from a basidium like A and 

 have been placed on malt-agar. B, before germination. C, a germ-tube has 

 been put out laterally. D, the conidium b at its base a has emitted the germ- 

 tube c. E, a primary conidium which has germinated at its base a, has become 

 septate and empty of protoplasm, and has given rise to a mycelium which has 

 produced secondary conidia (secondary basidiospores) c-e ; the protoplasm 

 of the mycelium is creeping into the secondary conidia and the mycelium is 

 becoming septate ; b, a spherical rudiment of a secondary conidium on the end 

 of its sterigma ; c, a full-grown secondary conidium into which protoplasm 

 is still passing ; d, a secondary conidium about to be discharged, a drop of 

 liquid has been excreted from its hilum within the last six seconds ; e, a 

 secondary conidium which along with its drop has just been shot away from the 

 sterigma /. Drawings based on experiments carried out by W. F. Hanna at 

 the Dominion Rust Research Laboratory. Magnification, 660. 



pairs of primary conidia from the promycelium, as in (4), is not 

 spontaneous but is effected by a mechanical shock and possibly by 

 wind pressure. It may be that, under natural conditions, the mode 

 of development just described and illustrated in Fig. Ill actually 

 takes place, but as yet it has not been observed. 



We may now consider the development of unconjugated primary 

 conidia, and here we encounter a sixth possible mode of development. 



