220 



which touch one another at their tips, become pitt»d oh the 

 conte.ct^ *i,lls, "the walls are reabsorbed, ths two guatd cells 

 thus appearing later as ring cells, v/hich serve less in clos- 

 ing the _ air passage, but rather stiffen it". In general the 

 galia do not abound in stomata, 1 kno.? of no cast^ as yet> in 

 which, then the epidermis makes an active surface growth, the 

 number of the stomata is increased in correspondance with th« 

 increase in surfcoe. Tho tisnue lying directly unc1e-r the stom- 

 ata often rboiftnds in Intorstiees and forms, at times, a snali 

 cushion on the top of which lies the stoma. 



Lentioels are especir.lly noticeable on the various IJeraatuS 

 galls of the v;lllow, The stom ata. together with the adjacent 

 parts of the epidermis, soon disintegrate r.nd large, roundish 

 lenticels develop beneath then, vhich as |rorm dots, often give 

 tbe galls a very characteristic appearance. The lenticels on 

 the galls of lema tus gaHrrlini on galix grandiflnra are especially- 

 large and nunerous. In Kenatus belluB ©ne or ttwo especially 

 large lenticels are present on that part of the f^rll which be- 

 longs to the upperside of the leaf. In moist air, lenticels de- 

 velop the excrescences already described ^tist like those of the 

 normal paTts, Aphla ga^ls also are at times rich in lentioels, 

 (258) ©specially those of Pemphigus spiro theoe and F. bur sari us, 'Sot 

 only the gs»;lls themselves, but even~flie adjacent parts 6t the 

 petioles and the midrib swell greatly st tines end develop 

 numerous lenticels, 



KustenmfH8hf?r has found holes in the. epidermis of var- 

 ious galls whi(3h he terms carbondioxid fismires. The car- 

 bon dioxid flsFurea are sirnply epidermal cells, ?/hich are 

 separated frim one another and between which the intercel- 

 lular space is open to the outer f.ir. ♦ They usually have 

 small lumlna and lie at points, where several cells touch 

 at the corners, The upper opening is usually three- 

 cornered", 



"I have named them carbon dioxid fissures, because I^ 

 think th6v ha.ve been produced by an inner pressure in an in- 

 tercellular space too far distant from other air passages, 

 which nressure is caused by the freeing of carbon dioxid 

 (loc. cit. p. 181)". 



According to Kustenmacher, under certain circumstances, 

 pores in the membrane can also discharge the functions of 

 pneumathodes , 



"The sieve hairs of the Cecidomyia gall, the normal 

 fascicular hair of Hierac^um and the heirs of the Perruginea 

 gall, are, according to Kustemmcher,- "organs which can 

 convey air into the interior of tbe cells". 



In these statements^ of course, it is only a question 

 of hypotheses, and. as I believe, very improbable ones. 



6. Secretions and Secretion Reservoirs 



The secreting elements of the norml epidermis and those 

 conveying the secretions, are either found again iit gall tissues 

 in an unchanged form, or a rich increase of the elements fur- 

 nishing the secretions takes place. Accoraing to Kustenmacher 

 in the formation 6f the Cecidomyia galls on Artemisia campentr-^s, 

 the oil ^^res of ni^raal plants act absolutely passively. Among 

 the galls of JIucaliptua, of which I investigated herbarium mater- 

 ial forms may be fotxnd which are practically free from secre- 

 tory pores, side by side with those whose parenchjTma is penetrAXcd 



