213 



If a well differentiated nutritive parenchjina follows, 

 on the inside, the irregular wood layers, the structure 

 must be cbnsidered to be a prosoplasraa; the gall of Syn - 

 oiohyus politus would thus be the only prosoplasniatlc one 

 with layers of libriform fibres. Howev.er, it shows essen- 

 tially the greatest correspondence ■ to kataplasraas and we 

 247) may term it a knarl ball produced by p;aii aninals . The 



^lovelopraental history ot' this gan, v/hich is not of rare 

 occurrence in Sicily, could not be studied in the apeci- 

 rnens at my disposal, A oloser Investigation of the re- 

 markable structure 'Vould be very desirable. 



In many galls the "tendency" to form thick v;nllod paron- 

 ohyma cells is vr^ry frreat and is no't thoroughly exhausted In 

 tho production of tho mechanical mantels just described. Galls 

 which contain sufficipnt quantities of thin-wallod bark paron- 

 chyma in young and medial stages of dovolopnent finally oonfslFt 

 only of scloreidp - at times after the disappoarance of the ten- 

 der nutritive tissue. An example of this is the large gall of 

 Cynips Mayri . in which tho luxuriant tisnue masses between the 

 outer rnd inner mechanical mantels finally become entirely 

 thl«k-walled and lignified (fig. 109). 



As In the consideration of normal parts of plants, it is 

 also not admisaable to consider here all thick-walled cells as 

 mechanically acting parts which function expediently. Besides, 

 the Bclereid tissue, produced late in many galls, is often so 

 porously constructed thiit there can be no thought of a mechan- 

 ically effective tiSvSue. 



(848) nevertheless, besides the above named sclerotic tissues, 



we find Still others which function very obviously as such and 

 deserve brief mention. 



I would name first of all the closing tissues, I thus term 

 those tissues which are used to assist in tightly closing the 

 entrance of the gall, because of their suitable cell forms. In 

 many walled galls, short, extraordinarily thick *-walled papillae 

 are produced on both sides of the entrance to the gall cavity, 

 and form a cogging of the two contact surfaces. Figure 110 

 shows part of a cross -sect ion through the gall of piplosis^bpt- 

 ularla, The papillae are short and rounded, apparenxly acting 

 Bimilarlir to the sane structures of the cone-scales in coni- 

 fers-*-. Since these peculiar hfiir structures in the botularia 

 gall are formed onlj?- on the surfabes touching one another and 

 in their immediate vicinity, it mi^ht be well to make investi- 

 gations as to v/hether locally acting stimuli (perhaps stimuli 

 of contact?) possibly cause their formation^. 



Further, the mechanisms 6S opening deserve our attention. 

 Many gall animals free themselves from their enclosures by eat- 

 ing their way out of their dwelling place. In others, the host 

 plant produces the necessary mechanisms which, at ihe time of 

 ripening, give the gall animals their freedom. The mechanism 

 is set in action as soon as the tissues of the gall begin tfe 



^ Tubeuf . Haarbildungen 4, Koniferen, Forstl,- Katurwiss. 

 Zeltschr,, 1896, Bd. V, p. 109. Compare plate VI, fig. 3, 



It might be possible tliat here, as well as in other gall' 

 formations, the chemical stimulus, arising from the gall poison, 

 participates only Indirectly in the prod\ictlon of definite 

 forms, since it only makes the tissues susceptible to other 

 kinds of stimuli. 



