101 



thorough., experimental investigation of the question, whether 

 in STich cases too great loss of water by transpiration ac- 

 tually incites hypertrophic growth, would be especially in- 

 teresting Since the only cases yet known are those in vfeich 

 aDnormally large cells are formed as a result of too slight 

 transpiration. Kie question whether tyloses of the air 

 Chambers are abli to decrease the water transpiration of 

 the leaves etc., in a way "expeitient" for the organism, 

 needs further investigation. Mn many cases the surface 

 transpiring moisture might rather be increased by the abnor»a 

 mal growth of the mesophyll cells. 



6. GALL HYPERTROPHIES 



Those hypertrophies, which we will term gall-hyper~ 

 trophies, have primarily a common etiological charaoteristio- 

 gall-hypertrophies are those v\3iich are produced by the ef- 

 fect of a poison given out by a foreign animal or vegetable 

 organism. 



Bie abnormal tissue products, histologically most 

 divers e^ produced by the influence of foreign organisms, are 

 differentiated from the corresponding normal tissues less by 

 the size of their cells than by their number and their pe- 

 culiar tissue differentiation. We will have to consider 

 these supplementarily when discussing hyper^Jlastic tissue 

 structures . (Chap. V). I will defer until then a few 

 general notes concerning galls, which are true alSo for the 

 forms produced only by a cell growth. A complete, sharp 

 line cannot be drawn in detail between hypertrophie and hy- 

 perplastic abnormal tissues even in those produced under the 

 influence of parasitic organisms, Hetherless I consider 

 that the difference emphasized here is a suitable foundation 

 for the division and that it makes possible the drawing up 

 of groups and sub-groups , which may be termed "natural" .ones 

 on account of their correspondence etiologically and hieto- 

 logioally. 



In deciding the individual cases, the same questions 

 are to be discussed as in the earlier groups;- questions as 

 to the form of the hypertrophied cells and their internal 

 structure. It must be shown that, in contrast to many other 

 hypertrophies, the formation of those induced by foreign 

 organisms is connected with an abundant supply of nutritive 

 materials, with an "over-nutrition" -sAfeich finds its obvious 

 expression in an enormous accumraulation of albumen, starch 

 ot the like. 



Gall-hypertrophies occur extraordinarily often in the 

 epidermal and fundamental tissues, in various plants and 

 under the influence of the various animal and vegetable par- 

 asites. 



a. E;fiidermis. 



In the next chapter it v;ill be shown repeatedly that 

 (108) the epidermal cells in general participate only moderately 

 in hyperplastic tissue formations; their "tendency" to cell 

 diYlsion is slight. In hypertrophies, however, the epidermal 

 cells play an important part. They are stimulated to growth 

 , by different kinds of parasites and furnish products of often 

 astounding size and aurprising diversity. 



