MILDEW. 



MILDEW. 



it would inflict on their crops. They con 

 si lered it as the instrument of vengeance di 

 reeled by a particular deity, to whom they ap- 

 plied the same appellation as to the disease 

 itself. (Schneider's Scriptorum Rei Rusticee, vol. i. 

 pt. ii. p. 246.) To propitiate this presiding 

 deity, a festival entitled Rubigalia, was institut- 

 ed by Numa in the eleventh year of his reign, 

 that is, 704 years before the birth of Christ. It 

 was celebrated annually on the 25th of April, 

 in the neighbourhood of a grove, at the fifth 

 milestone, on the Claudian Way, and comprised 

 sacrifices, races, and obscenities. Reddish- 

 coloured bitches (rnfce canes) were sacrificed, 

 because the lesser dog-star was then in the 

 heavens, and was considered unpropitious to 

 corn. (Plinii Hist. Plant, lib. xviii. c. 29 ; Varii 

 Flacci Facti, p. 63.) 



Ovid, who enters fully into the religious per- 

 formances of the festival, says, that the limbs 

 of a sheep and the entrails of a dog were 

 offered as a sacrifice on the occasion; and 

 that the priest informed him that he knew of 

 no reason for the latter animal being sacrificed, 

 but that its name coincided with that of the 

 constellation which at that season was appa- 

 rent in the sky. The prayer addressed by the 

 priest to the presiding deity marks so strongly 

 their knowledge of the extent and inducements 

 of the disease, that I shall give a nearly literal 

 translation of a part : 



"O, blighting Rubigo, spare the corn-plants. 

 And let the ear wave gently o'er the surface of the 



earth : 

 Suffer the crops which have been nourished by the 



propitious 

 Stars of heaven, to grow until they become fit for the 



sickle. 



Thine is no small power; the crops thou hast marked 

 The dispirited cultivator reckons as lost. 

 Neither winds, nor showers, so much injure the corn ; 

 Neither when bitten by the frost does it acquire a hue 



so pallid, 



As if the sun fervently heats the moist stalks ; 

 Then, O! dread goddess, is the opportunity for thy 



wrath; 

 Be merciful, I pray, and withhold your rusting hands 



from the crops ; 

 Nor harm the cultivated land : it is sufficient to be able 



to do harm." 



The misty weather, mistaken by the Roman 

 cultivators as actually a cloud of mildew, is 

 only one of many numerous instances which 

 might be quoted where causes of the disease 

 have been considered to be the disease itself. 

 To enumerate these would form a long cata- 

 logue of mistakes ; yet these I should not he- 

 sitate to detail, because the refutation would 

 incidentally introduce much useful informa- 

 tion, but that they will for the most part be 

 noticed among the circumstances which pro- 

 mote the occurrence and aid the progress of 

 this epidemic. 



The first person, I believe, who correctly 

 pointed out the nature of mildew, was Felice 

 Fontana, who, in the year 1767, published at 

 Lucca a very particular description of the fun- 

 gus occasioning it, in a work entitled " Osser- 

 vazione sopra la Ruggine del Grano." Since then 

 it has engaged the attention of many botanists, 

 and the results of their researches have been 

 to establish it as a distinct species of fungus, 

 though they differ as to the genus to which 

 they attach it. It is the Pucrinia graminis of 

 810 



Pcrsoon (Disp. t. 3, f. 3) ; and it is the Undo /ra- 

 menti of Sowerby. 



In Plate 2 there is a representation of this 

 fungi, in which 



I, is a portion of wheat-straw affected with 

 rust, magnified, to show the parasitic plant or 

 fungus, giving rise to the disease called rust, 

 blight, and mildew. 



m, Another portion of a diseased stem in a 

 green state, and before the fungus is quite ripe. 



n, The small portion marked 1 (1), still more 

 strongly magnified. 



o, p, 9, r, s, t, u, Very highly magnified repre- 

 sentations of the fungus parasite in different 

 stages of growth and maturity. 



o, Shows it in the young state ;p, full-grown; 

 q, two plants bursting and shedding their seeds 

 when under water in the microscope ; r, two 

 plants bursting in a dry place ; s, apparently 

 abortive ; t, seeds in a dry state ; u, a small 

 part of the bottom of a pore, with some of the 

 parasitic fungi growing upon it. 



Rust grows on the leaves and stems of wheat, 

 &c., appears in dense diffuse tufts, often con- 

 fluent, forming long, parallel lines on the culms ; 

 at first brownish-yellow, but changing to black. 

 Sporidia elongated, clavate, very slightly con- 

 stricted at the septum ; upper cell the shortest; 

 stipes filiform. It must not be confounded with 

 another parasitical fungus, which is common 

 upon the wheat-leaves and culms, but which is 

 not so injurious, namely, the Uredo rubigo, of De- 

 candolle (Flora Franca, vol. vi. p. S3). Charac- 

 terized by spots yellow ; heaps oval, scattered, 

 generally epiguous ; epidermis at length burst- 

 ing longitudinally; sporidia sub-globose, red- 

 brown, easily dispersed. If the straw of wheat 

 be examined with the assistance of a magnify- 

 ing glass, its striped surface will be seen to arise 

 from longitudinal partitions of the outer bark 

 or epidermis. The depressed partitions are 

 furnished throughout their length with 1 or 2 

 rows of pores or orifices, which seem capable 

 of emitting or imbibing moisture as the wants 

 of the plant may require. Similar pores, 

 though varying in form and arrangement, per- 

 vade the leaves and chaff, or glumes ; and it 

 's in these pores that the seeds of the parasiti- 

 cal Puccinice obtain admission, and, vegetating 

 'n the cavities to which they lead, doubtless 

 hrust their minute roots into the cellular tex- 

 ure beneath the bark, and intercept for their 

 own nourishment that sap which should pro- 

 ceed to the grain for its developement and 

 completion. The corn necessarily becomes 

 shrivelled, proportionally as the fungi are more 

 or less numerous on the plant: and as it is the 

 nutriment that would have perfected the inte- 

 rior of the grain, which is chiefly extracted 

 by the fungi, for the exterior form is nearly 

 completed before the mildew occurs, the pro- 

 portion of flour to bran is always much reduced. 

 Sir J. Banks observed, in 1804, which was a 

 mildew year," that some of the wheat would 

 not yield from a sack so much as a stone of 

 lour. 



Sir Humphry, then Mr. Davy, placed the 

 oss caused by this fungus beyond a doubt, 

 ?y chemical analysis. He found that 1000 

 parts of 



