1847.] Insects Injurious to Vegetation. 19 



far as a single experiment could do, that wheat might be mowed 

 at the former period without any diminution of its productiveness, 

 whilst at the latter, both the straw and heads would be of a more 

 slender and feeble growth. 



6. Flij proof wheats. — That there are any kinds of wheat which 

 are perfectly " fiy proof," (to use a common and expressive term,) 

 as has been sometimes stated, we wholly disbelieve. At times 

 when the fly is so excessively numerous as to attack barley and 

 rye, it is not probable that any of the cultivated species of the 

 genus Triiicum can entirely withstand its attacks. But that there 

 are kinds of this grain, that escape with little injury, when other 

 kinds are almost wholly destroyed, is a well established fact. 

 What the peculiar properties possessed by these varieties are, that 

 render them thus singularly invulnerable, has never been investi- 

 gated with that degree of accuracy which so interesting and im- 

 portant a subject well merits. Mr. Worth supposes that lly proof 

 wheats must have smooth leaves, afibrding no grooved or chan- 

 neled surface to hold the eggs of the fly. {Amer. Far., ii., 181. j 

 Mr. Smeltzer thinks the leaves of such wheat stand out horizon- 

 tally from the stem, or incline downwards, instead of being erect, 

 and that the egg is thus washed to the ground by rains. {Patent 

 Off. Report, 1844, p. 434.) The Hon. J. Taliaferro regards the 

 immunity as proceeding from the strength and vigor of the roots, 

 whereby the plant continues to grow, notwithstanding the ex- 

 haustion of its juices by the worm. (Patent Off\ Report, 1842, 

 App. No. 1.) This theory appears to us more plausible and more 

 in accordance with the facts recorded with regard to these varie- 

 ties, than any other Avhich has been proposed. Other opinions 

 less specific, might be alluded to, but all of them are opinions 

 merely, as w^e discover no evidence of their having been substan- 

 tiated by a diligent investigation of this point. The reputation 

 of the Undeuhill wheat has already been sufficiently shown. This 

 was a bearded white-chaff, with a plump yellow berry, requiring 

 to be thoroughly dried before grinding, and then producing flour 

 in quantity and quality equal to the best of the other varieties. 

 Its fly proof quality was by many supposed to be owing to the 

 hardness or solidity of its straw. The fly fieely deposited its eggs 

 upon this wheat, but it was seldom, if ever, materially injured by 

 it. The Spelter wheat [Triticum spelta, Linn.,) was also long 

 since remarked as never having been injured by the fiy. This is 

 so very inferior a species, that it is but little in use in this coun- 

 try, and only cultivated because it will grow well on the poorest 

 soils, whether the season be wet or dry, and is free from all mal- 

 adies. It has a long, slender, beardless head, with the chatf so 

 firmly attached to the grain, that it can only be separated by pass- 

 ing through a mill, and yields a yellowish flour. It is more high- 



