THE LEAF-SMUT OF TIMOTHY. 



41& 



grasses, which are finally reduced to brown slireds, covered witli 

 dusty si)ores. 



Tlio first ii])peiiriinco of tliis disease is in the 

 formation of lead -colored, thickened lines, 

 about l-O-i in. wide and 1-10 to J in. long, be- 

 tween the nerves of tlie leaf. The epidermis, 

 which at first covers them aiul gives them their 

 gray color, soon breaks away, revealing a ]>()W- 

 dery ma-s of black-brown spores, which are ir- 

 regularly rounded or egg-shaped, and closely 

 studded with short spines. They measure 10- 

 13 micro-millimeters, and in their microscop- 

 Fio. 159. ical characters closely resemble the spores of 



the corn-smut. 



Similar black lines are formed in the leaves of species of Ghjce- 

 ri(t l)y I's/i/dfjo I()Nf/i,ssiin(i (Sow.) which has smooth brown spores, 

 3.5 to 7 micro-millimeters in diameter, and in the leaves of wild 

 rye and other grasses by (^rori/sfis (iccidht. (Wall.) the dark 

 brown opaque spores of which measure l()-3() micro-millimeters, 

 and usually occur in clusters of 2-4, closely surrounded by masses 

 of half-round, colorless cells of slightly greater diameter. 



Ustilo(jo J/i//)(Kli/fes (Schl.) occurs on the stem of quack grass 

 and other species, usually forming black smut masses inside the 

 leaf -sheath, and T. (/nuidis (Fr.) causes cat-tail-like swellings on 

 the internodes of the reed. 



The fruit of many grasses is replaced by other smut fungi, the 

 number of which is very considerable. The commonest are: 

 Ustilago panici glauci (Wall.), very abundant in autumn on 

 pigeon grass; F. ruhenhnrstiana (Kuelm), on crab grasses and 

 sand burs; and l\ srr/efuiii, (P.), in oats, barley, wheat, etc. 



Draining the soil well, transferring the crops to new land 

 when they have begun to smut badly, and exercising care with 

 respect to manure are preventive measures. 



M(>. iHm.— TUUtia Dtrioi/urmu iu Timothy leaf; upurea at a; b. Urocu»t*» occuUut 

 «pores. 



