144 BOTANICAL GAZETTE. [J une ? 



I 



to 



the host tissues into which it seems to graduate is its reddish 

 brown color and its ability to resist the action of reagents, 



macerating fluids, etc. 



That the teleutospores are sub-epidermal at maturity is 

 apparently because of the fact that before they have become 

 strong enough to rupture and throw off the epidermis the 

 hyphse which arise on the sides of the young sorus have 

 fused with and hold that covering in place. 



Explanation of Plate XV.— Fig. 1. Vertical section through 

 teleuto-sorus of P. graminis Pers. on leaf sheath of Triticum vulgare; 

 host tissues in cross-section : a, epidermis ; b, teleutospore ; c, scleren- 

 chyma ; d, fungal hypha. X 120. 



Fig. 2. Vertical transverse section of young compound teleuto-sorus 

 of P. coronata Cda. on leaf of Avena sativa, showing the relation of the 

 young spores to the surrounding tissues and the penetration of the host 

 by the fungal hyphse : a, epidermis ; b, a portion of the spore- bed (stroma) 

 in section; c, the same as found between the simple sori, a so-called par- 

 aphysis in vertical longitudinal section ; d, young spores not yet septate ; 

 e, nearly mature spore ; /, beginning of stroma which finally encloses the 

 spores. X 350; section 5 m thick. 



Fig. 3. Portion of a vertical longitudinal section of leaf of Avena 

 sativa, showing very early stage of a teleuto-sorus and intercellular hy- 

 phse : a, epidermis ; 6, coalescing hyphse forming the spore-bed ; c, hypo- 

 dermal cell. 



Fig. 4. Tangential section of leaf of Avena sativa in hypodermal re- 

 gion passing through the young spore-beds : a, hypodermal cells; 6, basal 

 portions of young spores; c, intercellular hyphse; d, hyphse fused with 

 cell walls and partly in section. Section 5p thick; X350. 



Fig. 5. Apices of four mature spores of R coronata Cda. as seen from 

 above, showing form and position of digitate processes. X 680. 



Fig. 6. Spore and so called paraphysis in situ ; typical form from F. 

 rubigovera DC. on Hordeum jubatum : a, epidermis; b, teleutospore ; c 

 the "paraphysis" (stroma). X 350. 



Fig. 7. Two paraphyses from uredo-sorus of Phragmidium rosx-al- 

 pin* DC. X 350. 



Fig. 8. Portion of a compound sorus of P. anemones-virginiante Schw. 

 on Anemone patens, showing intersorial stroma in section, c-a; b, hypha 

 passing over apices of spores ; rf, hypha beneath the spore-bed ; stroma 

 and epidermis fused at a. X 200. 



Fig. 9. Same as fig. 8; hyphio which form the intersorial stroma not 

 completely fused : a, epidermis ; b, hypha ; c, spore. X 200. 



Fig. 10. Left corner of sorus of P* anemones-virginiaiuc J a, epidermis 

 of host; 6, hypha partly fused with epidermis; c, coalescing hypha; d, 

 spore. X 200. 



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