280 



FARMERS' REGISTER— SMUT, OR DUST BRAND. 



some samples which had been so prepared, and 

 washed in salt water, and declared to be perlectly 

 clean; but on my putting some of these purified 

 grains into water, in a watch-glass, and leaving 

 them to soak about twelve hours, on then bringing 

 them under the microscope I tbund many ol tlie 

 fungi floating on the water. This fact con- 

 vinces me tiiat mere cleansing is no secure pre- 

 ventive of this disease; and that the most eflica- 

 cious, and perhaps the only remedy for preventing 

 it, is that of depriving the seeds of the fungi ol' 

 their vitality. To efl'ect this, innumerable reme- 

 dies have been recommended, and I believe ap- 

 plied by the farmers, but have seldom proved en- 

 tirely successful. From my own often repeated 

 experiments, though on a limited scale, I ant con- 

 vinced that the best and surest remedy is to steep 

 the seed-wheat in properly prepared lime-water, 

 leaving it to soak at least twelve hours, and then 

 to dry it well in the air belbre sowing it; but I tear 

 that it will be ibund very difficult, if not impossible, 

 even by this method, to kill the seeds of the fungi 

 entirely, when the quantity of seed-corn is great; 

 and consequentlj^ some infected plants might still 

 be found in large fields. 



Steeping and properly drying the seed-corn in 

 the above manner, not only prevents the disease 

 arising from the infected seed-corn, but does also 

 elfectually prevent the clean seed from being in- 

 fected by the seed of the fungi, which might exist 

 in the soil of a field on which diseased wheat had 

 been growing before; and consequently the clean- 

 est samples of seed-wheat should be steeped, as 

 well as the most notoriously infected. 



These facts I have ascertained by repeated ex- 

 periments of strongly inoculating with the fungi 

 seed-corn which before had been properly steeped 

 and dried, and the result has always proved satis- 

 factory, for the infection never took place. 



Wheat is the only plant that is liable to be af- 

 fected by the Pepper Brand, which is occasioned 

 by the uredo fcetida. The Smut, or Dust Brand, 

 is also occasioned by an uredo, but of a decidedly 

 different species, 



r. B. 



Kew, February 21, 1833. 



THE SMUT, OR DUST BttAND. 



From the same. 



This disease, like the Smut Balls or Pepper 

 Brand, is occasioned by a very minute parasitic 

 fungus, of the gcnusuredo, which Persoon (in his 

 Synopsis MethodicaFungorum) notices as uredo 

 segetum. _ It is, however, of a decidedly diflerent 

 species from uredo fcetida, which occasions the 

 Smut Balls or Pepper Brand, illustrated in my for- 

 mer paper. 



The uredo scgetnm is distinguished from uredo 

 fcEtlda, not being much more than one-half the 

 size and by being peifectly scentless; whilst uredo 

 fcntida is characterized by an extremely oflensive 

 smell. The manner in which uredo segetum ads 

 upon the plants which it attacks is also very dif- 

 ferent, and the effect much more destructive than 

 that of uredo fcetida, which only attacks the grains 

 in which it vegetates, but seldom bursts; wliercas 

 the uredo segetum not only generally destroys the 

 whole ear, but even the leaves and stem. " Fur- 

 ther, uredo segetum attacks not only barley, but 

 wheat and oats; and I have been informed that 



other species of gramineae are subject to lis attacks, 

 but I have not yet found any such specimens. 



I have ascertained, by repeated experiments of 

 inoculation, that the seedof the fungi oi' uredo sege- 

 tum, like ihat of uredo fcetida, is absorbed by the 

 roots of the germinating seed-corn and, being so 

 extremely minute, is mixed with and propelled 

 by the circulating sap, and deposited in almost 

 every part, even in the cellular tissue of the plant 

 where these seeds continue to vegetate and multi- 

 [)Iy rapidly, as well as in every part of the plant 

 where there remains the least vitality. The 

 whole ear is often found entirely destroyed many 

 weeks before even the individual florets are quitd 

 developed, or the sound ears emerge from the hose. 

 Sometimes, but rarel}', the infection takes place 

 after the parts of fructification have been formed, 

 and even after fecundation has taken place; in that 

 case the progress of the disease can easily be ob- 

 served. The germen is generally the first at- 

 tacked, and found partially, or half filled with the 

 fungi then the pistlis, the stitrmas, the anthers; and 

 even the extremely tender filaments appear full of 

 black spots which are occasioned by small clusters 

 of these fungi, which vegetate and multiply so 

 rajiidly that in a few days the whole ear is com- 

 pletely filled. 



In oat-plants such late infection occurs more fre- 

 quently than in barley or wheat, and the whole 

 panicle ofien emerges from its hose, to all appear- 

 ance in a perfectl}* sound state, or perhaps with 

 only a few infected spickets at its base, but the in- 

 fection soon spreads visibly through the whole 

 panicle and over eveiy part of the plant; and even 

 when such a partially infected ear is separated 

 from the growing plant, the vegetation and multi- 

 plying of the fungi continue as long as any moisture 

 remains in that portion of the plant which has 

 been so separated. I once collected and cut off 

 several such partially infected ears, which I intend- 

 ed to preserve as specimens, and for that purpose 

 I laid them in brown paper to dry them: they were 

 accidentally mislaid, and did not come into my 

 hands again till after a period of six or seven' 

 months; when, on examination, I found that the" 

 whole specimens were consumed by the fungi. I 

 have not the least doubt that the seeds of the fungi 

 are shaken out by the wind; and that even many 

 infected ears and plants are thrown on the soil of a 

 field where such diseased plants have been grow- 

 ing, and that the fungi continue growing and 

 multiplying on the soil, like those on the paper, 

 until they become part of the soil, from which 

 they cannot be distinguished. 



I fear it vvill prove very diflicult to find an effi- 

 cient remedy to prevent, or even to check this de- 

 structive disease; and this fear seems strengthened 

 by the consideration ol the numerous remedies 

 suggested by many eminent authors, as well in 

 this countrj^ as on the continent. That the reme- 

 dies of these authors should have failed hi pro- 

 ducing the desired effects is not surprising to me, 

 for I find that the most eminent of them'^not only 

 confound two or three distinct diseases, but are to- 

 tally unacquainted with the real cause of any of 

 the diseases: for some consider them caused by 

 insects; some attribute them to blasts of the wind; 

 others consider the disease to be a corruption of 

 the sap of the plant. These, and many other causes, 

 equally erroneous, have been advanced; but I hope 

 thatj if it be admitted that the seeds of the parasitical 



