276 The Scottish Naturalist 



ISOTHEA Fr. 



1*291. Saligna Berk. On Sallow leaves. Cothall. May. 



Omitted in proper place. 



1292. Russula fellea Fr. Under Beech trees. Clunyhill, &c. Aug., Oct. 

 1*293. Nidularia conilucns Fr. & Nord. On a piece of decayed fir wood. 

 Forres. Aug., Sept. 



1294. Septoria Hydrocotyles Desm. On Hydrocotyle vulgaris. Rothie- 



murchus. Aug. 



1295. Peronospora Potentillie De By. On Alchemilla vulgaris. Rothie- 



murehus. Aug. 



SCOTTISH GALLS. 

 By Prof. J. W. H. TRAIL. 



{Continued from page 216.) 



ULMUS MONTANA Sm. :— 



a. Galls of Tetraneura Ulmi L. form rifle-bullet-shaped bodies 

 arising from the upper surface of the leaf (" So. Nat." K, p. 216). 



b. Galls of Schizoneura Ulmi L., consisting of fleshy distorted 

 revolute leaves, which shelter, in the pouch formed by them, a 

 large number of the Aphides, amidst a quantity of secretion 

 ("Sc. Nat.," V., p. 216). 



c. Mite-galls in the leaves, the work of Phytoptus. They are 

 very inconspicuous when young, but are readily detected after a 

 time by causing the leaf around them to die and to become brown 

 in spots about 4 or 5 mm. across, very closely resembling the spots 

 so frequently produced on leaves by fungi ; indeed it was while 

 examining the spots in search of fungi that I detected their true 

 cause. The young gall is lenticular in form, projecting very 

 slightly from both surfaces of the leaf, slightly more so below, 

 where the orifice is situated. The gall is usually from -5 to 2 -5 mm. 

 across, and is about twice as thick as the leaf around it ; but its 

 surface hardly differs from that of the leaf in colour, though it is 

 at times yellowish-green. However, in course of time the colour 

 changes through yellow to brown as the tissue dies. On 

 microscopic examination the palissade cells are seen to he hardly 

 altered, but the cells of the tissue below them become much 

 enlarged, and leave large interspaces among them ; and in the 

 interspaces the mites live. Before the fall of the leaves the mites 

 may be found crawling over them, having abandoned the galls 

 through the opening below. Frequently a leaf bears many galls ; 

 and on some trees hardly a leaf can be seen free from them. I 



