THE GRAPE PHYLLOXERA, 15 



specific interrelation and identity of the two types. I make this an- 

 nouncement with all the more pleasure, that for three years jjast, both 

 on vines growing out-doors and in pots in-doors, I had in vain at- 

 tempted to obtain the same result. 



PRACTICAL CONSIDERATIONS. 



The more Manifest and External Effects of the Phylloxera 

 Disease. — The result which follows the puncture of the root-louse is an 

 abnormal swelling, diifering rn form according to the particular part 

 and texture of the root. These swellings, which are generally com- 

 menced at the tips of the rootlets, where there is excess of plasmatic 

 and albuminous matter,^ eventually rot, and the lice forsake them and 

 betake themselves to fresh ones — the living tissue being necessary to 

 the existence of this as of all plant-lice. The decay affects the parts 

 adjacent to the swellings, and on the more fibrous roots cuts off the 

 supply of sap to all parts beyond. As these last decompose, the lice 

 congregate on the larger ones, until at last the root-system literally 

 wastes away. 



During the first year of attack there are scarcely any outward 

 manifestations of disease, though the fibrous roots, if examined, will 

 be found covered with nodosities, particularly in the latter part of the 

 growing season. The disease is then in its incipient stage. The sec- 

 ond year all these fibrous roots vanish, and the lice not only prevent 

 the formation of new ones, but, as just stated, settle on the larger roots, 

 which they injure by causing hypertrophy of the parts punctured, which 

 also eventually become disorganized and rot. At this stage the out- 

 ward symptoms of the disease first become manifest, in a sickly, yellow- 

 ish appearance of the leaf and a reduced growth of cane. As the roots 

 continue to decay, these symptoms become more acute, until by about 

 the third year the vine dies. Such is the course of the malady on 

 vines of the species vinifera^ when circumstances are favorable to the 

 increase of the pest. When the vine is about dying it is generally 

 impossible to discover the cause of the death, the lice, which had been 

 so numerous the first and second years of invasion, having left for fresh 

 pasturage. 



Mode of Spreading. — The gall-lice can only spread by traveling, 

 when newly hatched, from one vine to another; and, if this slow mode 

 of progression were the only one which the species is capable of, the 

 disease would be comparatively harmless. The root-lice, however, not 

 only travel underground along the interlocking roots of adjacent 

 vines, but crawl actively over the surface of the ground, or wing 

 their way from vine to vine, and from vineyard to vineyard. Doubts 

 have repeatedly been expressed by European writers as to the power 



' For a very minute and careful study of the pathological characteristics of these 

 swellmgs the reader may refer to Max-Cornu's excellent papers in the Comptes Rendus^ 

 for 1873, of the Paris Academic des Sciences. 



