lo ^j'ay. 19 io.] Smut of Maize and its Treatment. 291 



'j'his local infection of the voung and tender tissues, whether of the seed- 

 lii^g, or of the leaves and stems, or of the male and female flowers, mav 

 take place at any time during the g.rowing season and consequently cannot 

 be controlled. But, fortunately for us, the .smut so far found in Australia 

 is a different sort. It attacks the cobs and tassels (Figs, i and 2) and 

 is usually confined to them, but in exceptional cases a few patches of 

 smut may appear on the upper leaves or on the enveloping bracts (Fig. 3). 

 This smut also occurs in America, but it is rather uncommon there. As 

 Clinton, an American authority, says of it — "' This is one of our most 

 conspicuous, l)ut rather uncommon, smuts. It has been introduced into 

 this country, p.robablv from Europe." The explanation of this statement 

 is, that the same smut is found in Europe on sorghum, and it was probablv 

 introduced by means of this host-plant. Then it sj)read to maize, as 

 it is found on both plants in the United States, and now it has probablv 

 been introduced here from America, although net a nati\e of that countr\-. 



The importance of distinguishing which of the two maize smuts we 

 possess is evident, when it is realized that the one mav Ije amenable to 

 treatment and the other not. The two smuts will now be brieflv considered, 

 and naturally the one which occurs in Australia, and is' therefore at hand 

 for investigation, will receive most attention. The descrii)tion of the other 

 will enable any grower to recognize it when he sees it and to -take the 

 nece.ssarv measures for removing the diseased ])lants. 



I. — Head Smut of Maize. 



{Sorosporinm reiliau/im {K/ieJiu) MeAIp.) 



Ti^is smut receives its common name, because it is usually confined to 

 the head or ear. It is enclosed at tir.st in a pinkish or whitish skin which 

 soon ruptures in order to allow the escape of the spores. It is distinguished 

 from the American Corn Smut by not excessi\el\- enlarging the ears and 

 forming large smut-boils, bv generallv confining itself to the cobs and 

 tc'issels and not attacking the leaves and stems, and by the character of 

 the spores. To show how fundamental the difference is, the Head Smut 

 belongs to the genus Sorosporinm in which the spores are arranged in 

 clusters (Fig. 4) forming, particularly in the young stage, closely compacted 

 spore-balls, while the American Corn Smut belongs to Ustilago, in which 

 the spores are all separate and distinct. 



Diseased and Healthy Plants. 



When the smut is fully developed, it is very conspicuous, but even 

 before the spore-masses are expo.sed, it may be readilv detected. The 

 .smutted maize plant remains longer green than the healthy plant ; it is also 

 more brittle and easilv broken ; it is more succulent and very sweet to the 

 taste. If it appears on the tassel at the top, all the cobs beneath are 

 usuallv smutted, although in exceptional cases there may be an odd health \ 

 cob. b'ut the tassel mav also be perfectlv clean and all the cobs beneath 

 smutted. When the mode of infection is considered, it will be easily 

 understood how this happens, and not only mav entire cobs be clean on 

 an otherwi.se diseased plant, but only certain grains of a cob may produce 

 spores (Fig. 4). Both the tassel and the cob mav be only partially 

 smutted and even smut-pustules may be developed on the enveloping 



