2 i 2 The Scottish Naturalist. 



in September, 18S2- Eggs and young animals were common 

 enough in the galls at that season. 



HIERACIUM PILOSELLA L. :— 



(a) Galls of mites (Phytoptus), being inrolled leaf-margins, are 

 exeedingly common on the Links north of Aberdeen in autumn, 

 though local apparently. Frequently several of the leaves in a 

 rosette remain small, with the pale lower surface visible, owing to 

 the margins continuing to be closely involute from the base even 

 to the tip of the leaf usually, though at times only in spots here 

 and there. Not seldom almost every leaf on some of the smaller 

 plants is attacked, and the plant soon withers up. The affected 

 leaves are rather thick and fleshy, but are little altered in colour, 

 though conspicuous from the exposure of the lower surface. The 

 margins usually make one and a half or two turns, forming a tube 

 in which one finds a few mites. The inner tissues of the leaf are 

 very little altered, beyond being slightly hypertrophied in the 

 cellular tissues, and the epiderm is far less modified than in 

 L. autumnalis. The mites are of rather large size for the genus 

 Phytoptus. There are no hairs specially developed in the interior 

 of the tube. I had observed similar deformities on H. Pilosella 

 in Perthshire, and elsewhere in Scotland, before I had recognised 

 their origin. They have been recorded from Germany and 

 Switzerland (Thomas and Schlechtendal), and from Austria 

 (F. Loew). 



(6) Leaf-galls of Tyle?icJuts sp. ? They are very inconspicuous, 

 and consist of a spot in the leaf, usually towards the margin, about 

 2 to 4mm. across, irregular in outline, about twice as thick as a 

 healthy leaf, hence slightly prominent on both surfaces ; differing 

 but little in aspect from rest of leaf, except in being slightly paler, 

 or sometimes reddish-brown, in colour. 



The differences brought about by the gall-makers can be under- 

 stood only by a comparison with a healthy leaf in section. The 

 latter shows, from above downwards, the epiderm, then two or 

 three layers of rather closely packed palissade cells, elongated at 

 right angles to the surface, then two or three layers of irregularly 

 branched cells, elongated in directions nearly parallel to the 

 surface, and showing large intercellular spaces among them. 

 Among these cells lie the fibrovascular bundles, usually close 

 below the palissade layers . Then comes the lower epiderm, 

 bearing numerous and variable branched hairs. 



In the galls the loose mesophyll below the palissade layers 



