184 Sorosporium. 



wliicli, probably, gave rise to this view. They are probably the remains of 

 the enveloping hyphae, as they become detached and disappear on treat- 

 ment with caustic potash. (Plate XLIIL, Fig. 136). 



Spore formation. — In a cross-section there is a central mass of parenchy- 

 matous plant cells, which are penetrated by colourless hyphae towards the 

 outside. These give rise to a dense mass of olivaceous hyphae surrounding 

 the central core of plant tissue, and one portion of the hyphae becomes spore- 

 forming while the other remains sterile. The sterile portion forms strands 

 of pale-coloured hyphae radiating towards the circumference, which are 

 slender, elongated, and regularly and closely septate. Between the strands 

 of sterile hyphae there are colourless hyphae, at first twisted into balls, and 

 gradually these become definite, colourless spore-balls. They increase in 

 size, the cell-wall becomes clearly defined, assumes a dark-brown colour, and 

 the whole forms a fairly solid mass at the outside. The spores may partially 

 separate from each other and are mixed up with shreds of the tissue of the 

 ovary, and the broken-up remnants of the sterile hyphae. 



The structure is clearly seen in Plate XLIII., Figs. 132, 133, where from 

 the central core of plant tissue radiating strands of very fine septate fila- 

 ments proceed and form, as it were, so many compartments in which the rows 

 of spores are developed. The spores are seen in every stage of development, 

 from the minute colourless spore, then with transverse and radiating septa, 

 and finally as a dark-brown cluster of spores. 



(Plates XXV., XLIII.) 



Stipa. 

 42. Sorosporium tumefaciens McAlp. 



Sori attacking and destroying entire inflorescence while still partially 

 enclosed in sheathing blade. The entire panicle becomes swollen, 

 dirty white to brownish, rupturing irregularly to allow the escape 

 of the powdery spore-balls, up to 5 cm. in length. 



Spore-balls globose and ellipsoid, oblong or irregular, olivaceous 

 to dark-brown, 50-80 /^ long. 



Spores olivaceous to brownish, somewhat firmly united together, 

 globose to ellipsoid or slightly irregular, smooth, often guttulate, 

 especially when germinating, 8^10 i-i diam. or 8-10 x 6.5 -7.5 ju., 

 occasionally 11.5 /.i long. 

 On Stipa sp. and Stipa puhescens R. Br. 



Queensland — Near Cloncurry, May, 1909 (Robinson). 

 Sorosporium granulosum Ell. and Tracy, has been found on Stipa in 

 America, but the spores are much larger, being 12-17 /j. in length. A cross- 

 section of an infected inflorescence, taken near its base, shows numerous 

 vascular bundles completely surrounded by spore-balls, the younger and 

 immature being towards the centre. The outer tissue is soon ruptured by 

 the swelling spore-masses, which escape as a black powder, while the vascular 

 bundles project in the form of numerous brown strands. 



Germination. — This takes place readily in water, whether the spores are 

 placed on a slide or floating on water in a watch-glass. In twenty-four hours 

 numerous promycelia project from each spore-ball. They are hyaline, 

 elongated, slender, septate, and bearing conidia laterally as well as terminally. 

 The conidia are cylindrical, 6-10 j-i long. 



(Plate LIV.) 



