2 



On the Diseases of Wheat. 



tion to this subject, and that too at a season when so little time 

 ' was left for observation or experiment, I have very little to offer 

 which can in any way be considered an advance on the knowledge 

 already on record. 1 have, however, examined wheat infested by 

 five species of parasitic fungi ; by the ergot ; by the little animal- 

 cule which produces the ear-cockle or peppercorn ; and by the 

 wheat-midge. As I have been able to satisfy myself of the 

 accuracy of previous observers on many points connected with the 

 diseases occasioned by the attacks of these plants and animals, 

 I shall confine my report to an account of them. I must beg it 

 to be understood, that I am offering a very imperfect report of 

 what is really known on the sub j ect, and consequently that I can 

 only propose a very defective sketch of what it may be right to 

 attempt in making further experiments. — I have however thought 

 it better to give this report at once, rather than delay it for a 

 twelvemonth : for it cannot be before then that fresh opportunities 

 will have occurred for making more extensive observations. 



Section I. — Remarks on Parasitic Fungi. 



As I shall in the first place notice the diseases occasioned by 

 the attacks of parasitic fungi, a few general remarks upon the 

 habits of these plants may not be unacceptable to the agriculturist. 

 All fungi grow upon some kind of organized matter, none of them 

 deriving their nutriment directly from the soil, water, or the at- 

 mosphere, like other plants. They are of great importance in the 

 economy of nature, by assisting in the decomposition of decaying 

 or decayed animal and vegetable substances. A few of them 

 appear to grow upon healthy subjects, but these may possibly most 

 frequently have originated on a part where disease or decay had 

 already affected some alteration in the tissue ; and then, by spread- 

 ing rapidly from thence, they may afterwards occasion the decay 

 of other parts also. None of this tribe of plants attain to any 

 great size, when we compare them with many species of flowering 

 plants, or even with many of those of other neighbouring tribes, 

 (as the Ferns, &c.) which never flower. Among fungi we find 

 a multitude of extremely minute species, which it needs the skill 

 of an experienced microscopic observer to detect and examine ; 

 and it is also among the very lowest of the several groups, into which 

 these minute fungi are classed, that we must search for the few 

 species that produce the fatal diseases in corn we are about to 

 notice. But if these fungi are themselves so exceedingly small, 

 how much more so are those reproductive bodies, analogous to 

 the seeds of flowering plants, by which they are propagated and 

 multiplied! So very minute are these Sporules (as Botanists term 

 them), that they altogether escape observation by the naked eye. 



