59 



peradventure, the specific interrelation and identity of the two types. I make this announce- 

 ment with all the more pleasure, that for three years past, both on vines growing outdoors 

 and in pots in-doors, I had in vain attempted 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, diflFerent 

 in form, according to the particular part and texture of the root. These swellings, which are 

 generally commenced at the tips of the rootlets, where there is excess- of plasmatic and albu- 

 minous 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 

 aflfects the parts adjacent to the .swelling.^, and on the more fibrous roots cuts oflF 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 aro 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 .second 

 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 disea.se first become manifest, in a sickly, yellowish 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 crfurse of the malady on 

 vines of the species rini/era, when circumstances are favourable 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 travelling, when newly-hatched 

 from one vine to another ; and, if this slow mode of progression were the only one which the 

 Sfiecies is capable of, the disease would be comparatively harmless. The root-lice, however 

 not only travel under-ground 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 vinej'ard to 

 vineyard. I)oubts have been repeatedly expressed by European writers as to the power of 

 such a delicate and frail-winged fly to traverse the air to an) great distance. On the 27th of 

 September, 1873, the weather being quite warm and summer-like, with much moistuie in the 

 atmosphere, Mr. Riley witnessed the insect's power of fliiht. Some two hundred winged 

 individuals, that he had confined, became very restless and active, vigorously vibrating their 

 wings and beating about their glass cages. Upon opening the cages, the lice began to dart 

 away and were out of sight in a twinkle. They have been caught in spider-webs in Europe, 

 and captured by Mr. Riley on sheets of paper prepared with bird-lime and suspended in an 

 infested vineyard ; it is clear, then, that they can sustain flight for a considerable time under 

 favourable conditions, and with the assistance of the wind, they m^y bo wafted to great dis- 

 tances. These winged females are much more numerous in the fall of the year than has been 

 supposed by ^Entomologists. Wherever they settle, the few eggs which each carries are suflB- 

 cient to perpetuate the species, which, in the fullest sen.se, may be called contagious. 



'• Susceptibility of difff.kent Vines to the Disease. — As a means of coping 

 with the Phylloxera disease, a knowledge of the relative susceptibility of different varieties to 

 the attacks and injuries of the insect is of paramount importance. As is so frequently the 

 ease with injurious insects, and as we have a notable instance in the common Currant Aphis 

 (Aplii.-i L'ibesiiJ, which badly afi'ects the leaves of some of the Currants, but never touches the 

 Gooseberry which belongs to the same genus. The Phylloxera shows a preference for and 

 thrives best on certain species, and even di.scriminates between varieties ; or, what amounts 

 to the same thing, practically, .some varieties resist its attacks and enjoy a relative immunity 

 from its injuries. It would be useless, and certainly unnecessary here, to attempt to ascer- 

 tain the reason why certain vines thus enjoy exemption while others so readily succumb ; but 

 in a broad way it may be stated that there is a relation between the susceptibility of the vine 

 and the character of its roots — the slow-growing, more tender-wooded and consequently more 

 ten dor -rooted varieties succumbing most readily; the more vigorous powers resisting best." 



