70 SIXTH ANNUAL REPORT 



season precluded the possibility of any true oall-lice being about. I watched from day 

 to day, hoping to see this precious gall grow, and expecting soon to see others, until 

 at the expiration of three week, noticing no change, I began to fear that it was aborted, 

 and on subsequently plucking the leaf and examining it, it unfortunately proved so to 

 be. I have since continued to place young root-lice, of different generations, on the 

 imost inviting leaves, but have obtained no more galls. Unsatisfactory as this isolated 

 experience is, it is, nevertheless, highly interesting, and proves that while the young 

 root-lice are very reluctant to settle on the leaves, and seem incapable of producing 

 galls, certain individuals among them can do so. 



(13) For a very minute and careful study of the pathological characteristics of these 

 swellings, the reader may refer to Maxime Cornu's excellent papers in the Comptes 

 liendus, for 1873, and Memoires (xxii, No. G) of the Academie des Sciences, Paris. He 

 •corroborates, by detailed observations, the conclusions previously arrived at by Plan- 

 chon and his followers ; but, like too many of his countrymen, very generally ignores 

 observations made out of France, and consequently sometimes repeats as original, facts 

 recorded elsewhere with less of det^iil. He concludes that the Phylloxera is not nour- 

 ished by the sap of the plant, but by plasmatic material which the latter stores up. He 

 also concludes that the swellings are produced solely by the mechanical action of the 

 tongue, and that they in themselves are the cause of the trouble, by absorbing in their 

 ■development, the nourishment needed for the vine, and by affecting, in rotting, the 

 parts not touched by Phylloxera : in other words, that the amount of nourishment 

 appropriated by the lice would never seriously affect the vine, were it not for the char- 

 acteristic and intrinsic swellings. I can not accept the last two conclusions. There is 

 n strong a priori probability that the swellings are due to something more than mere 

 mechanical action — to some poisonous excretive fluid, as in many gall-flies [Cynipidce) 

 and saw-flies {Tenthredinidm); or to some irritating and poisonous property of the pro- 

 boscis, as in the spines and hairs of many larva^-. We may not be able to analyze it, 

 'but it is difficult to understand how, without some such poisonous property, the Phyl- 

 loxera leaf-gall is developed, while so many other plant-lice perform similar mechani- 

 cal acts to that performed by Phylloxera without causing abnormal growths on the 

 plants they infest. Bearing in mind also, the withering and blasting effects which 

 many plant-lice and bark-lice cause to plants which never swell abnormally from their 

 punctures, it would seem obvious that with the vine roots covered with Phylloxera, 

 ■most of them rapidly developing and multiplying, the direct loss of plant substance 

 must be very material — however great the indirect loss through the swellings maybe. 

 There are any number of plant-lice no larger than our Phylloxera, and which there is 

 every reason to believe appropriate no more for the nourishment of their bodies, which 

 nevertheless affect most seriously the plants they inhabit by direct sucking of the plant 

 juices. 



(14) THE TKUK GItArK-VlNES OF THE I KITED STATES. 



BY 1>U. a. ENGELMANN. 



The Grape-vines are among the most variable plants, not only through cultivation 

 by which numberless varieties have been produced, but even in their wild state, in 

 which climate, soil, shade, humidity, and perhaps also natural hybridization, have 

 originated such a multiplicity and such an intermixture of forms, that it is most diffi- 

 •cult to recognize the original types and to refer the different given forms to their pro- 

 per alliances. Only by carefully studying a large number of forms from all parts of 

 the country, in their peculiar mode of growth, and especially their fructification, or 



