Lilipiitimt Enemies. 285 



covered with R. lacerata, its surrounding membrane prolonged into deli- 

 cate lacerate teeth, which studded the whole fruit with soft white points, 

 while the felty skin was timed orange gold with its constantly dropping 

 spores. Another closely-related genus is Cystopus, which has white spores. 

 It appears in oblong or linear white blotches on the leaves, and attacks 

 cruciferous plants ; among them, cabbages. The Polygona are some- 

 times almost covered with C. candidus. 



But the above-mentioned genera, though close allies, are far less injuri- 

 ous than the black-spored forms. These latter have been, for centuries, the 

 pests of farmers. They are similar to Uredo in their general mode of 

 growth \ but their ravages are more extensive and fatal. The bunt of wheat 

 ( Tilletia caries) takes possession of the whole grain, turning it into a mass 

 of black dust. It does not, like Uredo, simply grow beneath the epidermis 

 in a superficial manner : it permeates the whole substance of the grain, pro- 

 ducing its powdery spores with immense rapidity and profusion. Ustilago 

 Segetiim, the smut of all the cereals, infests the stems, leaves, rachis, and 

 grain. It grows within the tissues of the plant ; its spores finally bursting 

 forth in such vast quantities as to cover it with their jet-black powder, 

 which is simply an immense mass of black globules. The rapidity of 

 growth which will allow of the production from the apices of minute fila- 

 ments of this dense volume of cells is certainly amazing. The number 

 of them contained in an ear of smutty corn is simply inconceivable. They 

 utterly vitiate the plant they infest, turning it into a dust, which, when 

 moistened, becomes a disgusting inky mass. U. Mayidis, a kindred 

 species, infests Indian corn. 



Another genus, containing some of the most beautiful objects under the 

 microscope, but ugly enough in the farmer's eye, is Puccinea. Many of its 

 species attack plants of all orders, appearing in little dark, rounded spots 

 on their leaves. But tlie dreaded species is the wheat-mildew, Pucc'mea 

 graminis. This infests all cereals, attacking their culms and leaves. The 

 spores of this genus are larger than those of the other genera : they can 

 be almost individualized by the naked eye. They are borne on slender, 

 diaphanous, elongated cells, and are variously ornamented by surface 

 corrugations. They burst, like the others, from beneath the epidermis of 



