1-7 mm. long. This, in the ripe smut gall, consists of a 

 central core of host tissue coated by the spore mass, which is 

 bounded externally by the usual white skin seen in Cintractias. 

 As is well known, the normal female inflorescence of 

 Spintfex hirsutus is a large globular head, consisting of 

 radiating spines, 40 cms., or even more, in diameter. This 

 is borne, terminally, on a stout erect stem, and below it is 

 one, or sometimes two, small lateral groups of secondary axes, 

 bearingf flowers. The head itself is not more than 4 or 5 cms. 

 above the node below, and when ripe is readily detached by 

 snapping off the axis at an absciss region immediately above 

 the node. It then blows away, distributing the fruits as it 

 breaks up. The head is a complicated system of secondary 

 axes, arising in the axils of chaffy bracts, about 8 cms. long. 

 The majority of these axes are long tapering spines, averaging 

 '17 cms. (13'5-20 cms.), which are sterile. They are borne 

 in groups of 6-12 or more, each group representing a branch 

 system with exceedingly short intemodes. These spines form 

 the spring-like ''legs" of the tumble weed, and are a most 

 characteristic feature of the plant. In each group of sterile 

 spines are a few (1-4) shorter and stouter spines, 10-12 cms. 

 long (text fig. 2). These are the fertile secondary axes, each 

 of which has a single spikelet at its extreme base. The spikelet 

 consists of three sterile glumes (or two sterile and one abortive 

 male flower) and one fertile glume. The flower has glume, 

 pale, three stamens with minute anthers borne on filaments 

 as long as the ripe grain, and an ovary. 



The diseased female inflorescence is strikingly different 



from the normal (pi. i., fig. 2). The main differences are: — 



(a) Elongation of the internode below the terminal head. 



(h) Complete absence of the long sterile spines which are 

 so obvious in the normal inflorescence. A few 

 sterile spines may be present, but these are shorter 

 than the fertile spines, of which the head is largely 

 built up. 



(c) The spikelets are borne l'5-4 cms. above the base of 

 the fertile secondary axes, which are half as long 

 again as normal, i.e., up to 15 cms. 



The smutted female spikelet consists of two sterile glumes 

 and two fertile. Both the florets are much modified by the 

 fungus (text fig. 4), but the modifications are the same in each 

 flower, i.e., the lower floret, normally an abortive male, 

 behaves like a female. The florets have glume and pale, both 

 longer than usual, the latter being often involved in the smut 

 gall. No stamens have been recognized, the whole of each 

 floral axis above the pale being one elongate, rarely bifurcate, 

 smutty mass (text fig. 5). 



