1 84 AXXALS OF SCOTTISH NATURAL HISTORY 



Wissenschaften " of Vienna, xcvii. pp. 597-6O5), of which I 

 prepared a translation for the " Scottish Naturalist," 1889, pp. 

 114-121. He describes in it the results of many experiments 

 on infecting numerous plants of the orders Valerianacece and 

 Cruciferce, and a few from other orders, by laying on them 

 portions of Valeriana tripteris, found wild near Innsbruck, 

 the buds of which were infested by Phytoptus. These results, 

 he believed, prove that the same mites can gall in various 

 ways many kinds of plants. Professor Dalla Torre of Inns- 

 bruck has also put on record an observation of Professor 

 Heinricher, that willow twigs with buds galled by Phytoptus 

 having been used as supports for Polygala myrtifolia, the 

 latter after a time had its buds similarly galled. 



Phytopto-cecidia chiefly belong to the types described 

 above as Hair-galls (Erincum\ Roll-galls, Pouch-galls (from 

 the shallowest form of pouch to the slender nail form), 

 Blister-galls (the mites boring into tissues of leaves or bark 

 of twigs, but keeping the passage open), and Bud-galls. 

 These forms pass into one another frequently. They may 

 be restricted to limited portions of a member of the host, e.g. 

 on the leaves ; or they may affect almost every member on 

 a shoot, passing into the bud-galls ; or they may habitually 

 affect the buds only,as in Black Currant and Hazel ; orthe buds 

 may grow into short twigs with many lateral buds, causing 

 small "witch-besoms." If the flower-buds are attacked they 

 may become virescent, or may form large diseased masses, as 

 in the Ash, or may be otherwise distorted. Mite-galls show 

 little if any advance in complexity of structure beyond the 

 normal tissues. Any change is rather in the nature of 

 degeneration of tissues. 



ENTOMOCECIDIA is the name given to all galls formed 

 by insects. But they are so numerous and so varied in 

 structure that they are divided into the several groups to 

 which the makers belong. 



HEMIPTERO-CECIDIA. The division Hemiptera includes 

 a considerable number of gall-makers ; but of those in 

 Europe only one genus (Laccomotopus, galling the flowers of 

 Teucrium} belongs to the Heteroptera or Plant-bugs. All 

 the others belong to the Homoptera. The Psyllidce are 

 small leaf -hoppers, many of which produce pouches on 



