ON THJS A11A1SLE LAND

474

been occasioned by tlie circumstances of the weather men-tioned above as productive of both. In the Appendix NO. III.to the Agricultural Report of Berwickshire, a series of ques-tions regarding this subject are inserted, which were circu-lated in 1808 by Sir John Sinclair , with such answers bythe reporter, as he was able to make at the time. Havingseen no reason since to alter his opinions on that heath thefollowing description of that complicated and destructive dis-ease has been abstracted from his answers to these queries.

“ From the best information I can procure, the mildewbegan to make its appearance on the straw and ears of thegrowing wheats, immediately subsequent to a heavy fog ormist, rising as it were out of the ground, about the 4th tothe 10th of July 1808, and which was followed for severalweeks by much misty and rainy weather, attended by consi-derable heat and very little wind. The peculiar fog or mistabove alluded to, is called ground-rook in some parts of Scot-land , and strongly resembles a thick smoke which appears torise from the surface of the earth. The disease upon thewheat-straw, here called mildew, and which occasioned somuch injury, consisted of a species of lichen, of an oblongpointed form, like a wherry or canoe, having narrow whiteedges, and a black pulverulent disc; each individual spot or:plant being about an eighth of an inch long, and about a six-teenth in breadth. I can only say from memory, that it exact-ly resembles the figures and description given by Sir JosephBanks , as I had not then his excellent publication on the sub-ject to compare them accurately. The species of lichenwhich constitutes the disease of mildew, when growing a-bundantly on the straw and ears of wheat, must necessarilybe procured from its own peculiar seed, which seed accord-ingly is the immediate cause or origin of the disease. Butwhy this lichen should so abound in some years and not inothers, and why the particular weather which has been de-scribed as immediately preceding the appearance of the mil?