105 



Iiandois^ Thomas, Brioski^ Prank, Appel and. others.-^ The 

 studies of Nalepa threw light primarily on the diverse forms 

 of tRe parasites.*^ 



Erineum halts always form more or less thick turf- 

 like groups for vihich there is no definite external form 

 or definite size- proportions. 



It. is common foi" all Brineum structures that the 

 outer walls of the epidermal cells either take part en- 

 tirely in the growth of these cftlls or predominantly. Thus 

 it is evident that the hypertrophied cell cannot display 

 an enlarged reproduction of the normal epidermal cell, but 

 a change of its cell proportions mast be associated with the 

 increase in its volurane. 



In the simplest case, short papillae are produced 

 by the " out-pushinST of the epidermal cells. If the growth 

 of these cells continues, sac-like hairs are produced; slend- 

 er, cylindrical forms with rounded tips, or- club-like, dis- 

 tended ones with slender bosses and spherical or mushroom«- 

 like hS8fts« 



(112) Erineum galls with papillae^like elements are rare. 



Of course the sac««like hypertrophied cells undergo a paj)- 

 illae-»like first atage.. One may even see at times on the 

 edge of the Erineum turf that the growth of the individual 

 elements stops permanently in the papillae* stage. Only rare- 

 ly is the matured turf composed throughout of papillae-like 

 elements. An eixample is pictured in fig. 37. A piece of 

 the l?lade of Stipa pennata is illustrated; at a the epider- 

 mal cells have been incited to hypertrophy by PEytoptus mites 



1. Si0bold, Ber. Schles. Ges. Vaterland. Kulture, Entomolog, 

 Sektion^ 1850, p. 88. Landois, Eine Milbe (Phytoptus Vitis, 

 Land;) als Ursache des Traubenmisswachses. Ztsch. f. wiss. 

 Zool, 1864, Bd. XIV, p. 363. Thomas, Pr. as the most impor- 

 tant of his works shauld be mentioned-Ueber Phytoptus 3Juj. u 

 eine grossere Anzahl neuer od. v/enig gekannter Missbildungen 

 u. s, f. Ztsch. f. d. ges. Naturwiss., 1859, Bd. XXXIII, 

 J. 314. Zur Entstehung d. Milbengallen u. verwandter Pflan- 

 zenauswuchse, Bot. Zeitg. , 1878, Bd. XXX, p. 281. Entwickel- 

 ungsgeschichte aweier Phytoptusgallen an Pruiius. Ztsch. f. 

 d, ges , Naturwiss., 1872, Id. XXXIX, p. 193, Beitre, z. 

 Kenntn, der Milbengallen u. Gallenmilben. Ibid. 1873, Bd. 

 XLII, p. 613. Aeltereu. neue Beob. ub. Phytoptocedidien. 

 Ibid., le^-SS, Bd. 5IiIX, p. 329. Briosi, Siilia Phytoptosi della 

 vite, H, Giorn. Bot. 'Ital. 1877, Vol. IX, p. 23. Compare 

 Just»s Jahresber., 1876, Bd. V, p. 1234. Pr&nk krankh. d. 

 Pfl,, 1, Aufl. 1880, p. 671, 2. Aufl., 1896, Bd. Ill, p. 

 40ff, Appel, Ueber Phyto- und Zoomorphosen, Konigsberg, 

 1899, p, 41. 



" "irSi'EzunpBef I^XKalT^tiss ; '"tiefirma'eii^naturw; "KIT '1859; 

 Bd. XOVIII, Abt. 1, p. 112, 1890, Bd. XCIX, Abt. 1, p. 40 and 

 later, numerous supplements have appeared in place mentioned. 

 Of the older zoological literBttre, I will name only the works 

 of Bujardin (Ann* Sc. Hat» 1851 .p. 166) who founded the genus 

 Phytoptus, and Pagenstecher (Ueb. Milben, bes. die Gattung 

 Phytoptus. Verh. naturhist-mediz.Ver. Heidelberg, Bd, I, p. 46, 

 Ueb. Phyt. Tiliarum, Ibid. Bd. HI, p. 163), 



