Ustilagiiiacca. 141 



Just as ill the family of the Tstilaginacete, the oeuus Ustilago is the 

 startino; point for a number of distinct genera, so in the family of the 

 TilletiacefB there are clustered around the genus Tilletia a number of distinct 

 types. AVhile the spores are simple in Tillelia, they may unite to form 

 permanent spore-balls as in Vrocystis, the spore-balls consisting of an 

 envelope of sterile cells surrounding one or several fertile spores. The spore 

 masses, instead of being powdery and erumpent, may be permanently 

 imbedded in the tissues. When the spores are simple and scattered through 

 the substance of the tissues, this constitutes the genus Entyloma, but in some 

 of the species the spores have a tendency to adhere irregularly in groups. 

 This leads up to the spores being in balls as in Doassansia, where the spore- 

 balls have a covering of sterile cells for the fertile spores. 



The ten genera noted above are those which are definitely known to occur 

 in Australia, but it will give us a wider outlook if we glance at the principal 

 genera contained in the order as a whole. It is not so easy to settle what 

 genera should be included in such a survey. A number have to be excluded, 

 because they are now known to belong to other groups, and several have 

 been proposed which are hardly sufficiently distinct from existing genera. 



There are altogether nineteen genera, which may be arranged according 

 to their outstanding features — whether the spores are single or in groups, 

 whether exposed or imbedded in the tissues, whether the spore-balls are 

 temporary or permanent, whether there are sterile cells at the centre or 

 circumference of the l)all, and finally the mode of formation of the spores and 

 their oermination. 



USTILAGINACE/E Tul. 

 8ori usually forming exposed powdery or agglutinated masses. Germina- 

 tion by means of a septate promycelium producing lateral and terminal 

 conidia or sometimes by means of an elongated germinal tube without 

 conidia. 



I. Spores, single — 



A. Sori powdery at maturity. 



1. Ustilago. — Oermination by 1-5 celh-d promyceliuin with lateral 



and terminal conidia, or sometimes developing directly into 

 a mycelium. 



B. Sori agglutinated at maturit}-. 



a. Spores developed in a basipetal manner in liyphae 



arising from a persistent my<olium surrounding a 

 central columella. 



2. Cintractia. — Germination similar to that of Ustilago. 



b. Spores formed in chambers inside the host-plant. 



3. Mclanopsichiiin). — Germination as in rshlago. 



1 Spores chiefly in pairs — 



A. Sori powdery, 



0. Sori usur.liy inside peduncles. 



4. Mijkosi/rinx. — Germination not known. 



B. Sori agglutinated. 



a. Sori usually on leaves. 



5. »Sc/»'sone//^/.— Germination as in Ustilaao. 



