188 



excrescences of shrub or nestlike habit of growth. In 

 jjhich is involved an over-production of whole organs/ 

 Questions of morphological interest are eepeeialfy con- 

 nected with these. fOompare Goebel, Organographle ) . 



n^nfl,i!?l'^f ^}V^ -^ find Mycocecldia. 7/itches brooms are 



;^ L^nf^ ""f^r ?"^^o*?:0" ^y Exoascaceae, on Abies species, 

 on Acacia and Berber is by the action of various 5eoidiae, 

 0^ IMjoglig^olabrata by Oae omo aeforman s etc. Among the 

 Zooeocidiae fT or instance ,^Re f}bn6rrnal' ramifications of 

 the Syringa shrubs attacked by tbe mlte-disease, bear a 

 greqt similarity to the above mentioned fungus galls. 

 Giesenhr.gen-^ has shown that the formation of witches-brooms 

 doos not always proceed from normal buds but can also be 

 produced from loaves as adventive formations, (Taphrina on 

 ferns). Studied macrosoopioally, many forms of the witohea- 

 ftrooms may be recognized as "arrested developments". Thus, 

 according to Tubeiif, the witches broom of Oaeoma de for mane 

 consists of leafless branches-^^. According to eiesenhageh: 

 i^eshy, wart-like or antlor-like forms, always entirely 

 leafless, which are traversed by a vascular -bundle cord, 

 are produced by ^aphr lna Cornu corvl on the leaves of 

 Aspidium aristatiW. investigated iilcroeoopically, all 

 witches-orooms chow the characteristics of kataplasmatic 

 galls. The different tissue forms, of which the abnormal 

 branchlets and their leaves are composed, remain below the 

 corresponding normal tissues in differentiation. 



Some arrestment phenomena correspond to those already 

 descritjed (p. 32). The witches -brooms of the pitch pine 

 caused by Ae oidium elatintro bear neodle s, the hypodermis 

 of v/hioh remains und eve lope d and the mesophyll homogeneous. 

 The defeiopraent of bark fibres in the trunk is retarded, 

 but that of the parenchjmiatic elements, on the contrary, 

 is greatly favored. The pith !& abnormally abundant, the 

 bark perhaps twice as thick as in normal parts, also the 

 number of resin-canals is abnormally large*. Hesin-canals 

 may occur even in wood., which in th-e spruce v/ould have 

 none normally, through the action of the witches-broom 

 fungus°. The anatomical conditions of the Exoasceae -wit- 

 ches brooms^ are of a similar nature. The parenchymatous 

 tissues,- pith, hypodermis - are greatly increased, wood 



^ Ueb. Hexenbesnn an tropischen Parnen, Hora, 1892, Bd. 



LZXVI, p, 130. 

 2 



In this they resemble the cyjbinder-gnarls of- Ginkgo, 

 described above p. 185, 



^ The antler-llke malformations described by Miquel (Lln- 

 naeQ 1853. Bd. XXVI, p, 285) are, according to Sdlras*I.aubach, 

 deformed leaves of a Hemiptera gall (Ann. J. Bot, Bultenzorg, 

 1887, Vol, VI, P, 88), . 



* Acoordittg to Hartmann, Pr, Anatom, Vergl. d. H«xenbesen 

 d". Weisstanne mit den norm, Sprossen derselben. Dissertation 

 Freiburg 1, Br., 1892. Anderson^ loc.cit.also DeBary, Ueb; d, 

 Krebs u.d'.Hexenbosen d, We is st anna, Bot « Ztg. ,1867,Ba.JtA.v,p, «jo^. 



^ Cfi Mer and Andei^son loc, cit, 



^ Of. Rathay, E. , Ueb. d. Hexenbesen d. Kir schbaume , etc, 

 Sitzungsber. Akad. Wissensch. Wien, 1B81, Bd. LXXXIIX, 1. ADt;. 

 p. 267 and especially Smith loc, cit. 



