[page] 659

RUST IN WHEAT.

IT was good advice which I once heard given by a dealer in objects of natural history to a friend who had offered to procure specimens for him in some foreign country he was about to visit—"If you really wish to serve me," said he, "do not send me pretty specimens, nor yet anything that you may fancy particularly curious. I am already overstocked with such objects. Just keep a jar at hand, filled with spirits of wine, or gin, and whenever you see some very common-looking reptile or insect, pop it into the jar. The chances are, that everything you may consider least worth preserving will be of most service to me." The fact is, that persons who are not naturalists are no judges of what objects are most likely to be of interest in a strictly scientific point of view. Botanists would rather receive one of our most common weeds from a newly-discovered or newly-explored country than a new species of an already known genus. There are higher departments of botany than mere collectors of specimens are aware of. To ascertain the geographical distribution of a well-known species is a point of vastly superior interest to the mere acquisition of a rare specimen. My friend Darwin well understood this (but then he is an accomplished naturalist), when he so often stepped aside from his geological and zoological pursuits, to preserve specimens of plants for me; though botany formed no portion of his immediate studies. I suppose there are few persons possessing a healthy taste for the details of real adventure, who have not by this time read his most interesting "Journal of the Voyage of the Beagle;" and from what they must there have seen of his appetite for observation, they will not be surprised to hear that I have just received from him two blighted ears of Wheat, which few persons would have thought it worth while to carry with them round the world, but which he brought home upon the chance of their affording some information on the cause of those extraordinary and devastating blights to which the crops are occasionally subject in South America. As the memorandum he has made upon the subject will possess an interest in the eyes of agriculturists, I shall here present it to your readers; and then mention the cause to which these blights must be ascribed:—

MR. DARWIN'S MEMORANDUM.¹

                   "Northern Bank of the Plata, Nov. 20-30, 1833.

"No. 1593.—Bearded Wheat materially injured by a blight, called the 'Polvillo.' When a field is attacked, it seems, even at a distance, burnt up, and of a red appearance. On walking amongst the Corn, the shoes and trowsers become covered with a fine rust-coloured powder: hence the name. The powder is lodged in minute oblong patches, beneath the epidermis, which may at first be seen partially raised, and forming a scale. It attacks all parts indiscriminately. If the leaves are a little infected, the grains of Corn are light and dry; but if the ear and stalk are attacked, the crop is entirely spoilt. The blight is not observed before the grain is pretty full; and its attacks are very rapid—three or four days being sufficient to spoil a whole field. It is endemic in the whole district, though not equally destructive throughout. From this cause, last year, when the weather was wet, no grain was gathered. Hence an immense importation of flour took place from North America. This year, the weather being fine and dry, the blight will destroy or injure the greater part of all the crops. Fields thrown up in Buts, clear of weeds, on high ground, are equally attacked with those of less favoured aspect. It is here attributed to the sun's action after heavy dews. Crops grown from grain of the country, from the Cape of Good Hope, and from Rio Negro in Patagonia, were all more or less affected. It is remarkable that the Wheat at Rio Negro itself (which is grown on low diluvial lands) produced, even last year, its immense crop uninjured. This blight is a prodigious evil to the country, and most mortifying to the agriculturist, who does not know that all his labour will be lost, till within a week or fortnight of the time when he was expecting to reap the fruits of it."

This account of Mr. Darwin's would alone have inclined me to suppose that he was describing an example of a very virulent attack of rust or red-gum, a form of fungus which I have noticed in the Journal of the Royal Agricultural Society, vol. ii. p. 9, and again at p. 220, where I have endeavoured to prove its specific identity with mildew. The two forms of rust with which we are acquainted in England have been termed Uredo rubigo and Uredo linearis; and it should seem that the form which ravages the banks of the Plata is the latter, for I sent one of the two specimens with which Mr. Darwin supplied me to the Rev. M. Berkely,² who is far better authority on such a point than myself, or than any one else in this country. His remarks are as follows:—"Your rust appears to me the same with what I have received from Ohio, and agrees with our European species, which is referred to U. linearis, distinguished from U. rubigo vera by its longer spores, and by the more inflated cuticle of the sori. I believe U. rubigo vera to be the young of the common mildew. I have never myself gathered U. linearis. The La Plata specimen exhibits plainly the myceloid base. I have also U. rubigo vera from Ohio with the European characters." — J. S. Henslow, Hitcham, Sept. 9.

¹ Darwin's note is No. 1593 in his Beagle specimen notes. See Zoology notes, p. 394 and Porter 1987, p. 174.

² Miles Joseph Berkeley (1803-1889), clergyman, botanist and expert on British fungi.