249 



I call attention again to the bacteria w'hiCh developing nor- 

 mally, otily become rod-like cells, the involution forms of 

 which, hov-ever, seem to have been most diiirersely" sv;ollen, 

 tv7isted or 'branched, The form of abnormal cel3.s, rs v.ell as 

 their siae, has fxoe scope for development vhioh may be said to 

 b© .unlimited, The notev/orthy Erineum hairs (Fig, 40), the two- 

 ormed trichon of the gall of Meurotertis nnmismat is (Fig, 102) 

 and many others prove that the same holds good for higher plants. 

 Under normal conditions cells of this form are never produced 

 on the plants bearing the Erineum nor on the host plant of the 

 nuraismatis gall, 



;7e can thus affirm that the intensity, the localization, 

 the direction of the membrane grorrbh and thereby the form of 

 the- cell, are determined by the sum of all the factors which 

 act (internally and externally) on the cell and thrt under abnor- 

 mal conditions fnev" oelloforms can actually be produced, 



3, Inner Structure of the Cells 



■ ' " ■' 'Ill I ' ' ' ' " 



Only by considering the inner structure of the cells, will 

 v/e become acquainted v;ith the limits which, even under abnormal 

 conditions, ipemain decisive for the development of plant cells. 



In the last three chapters, repeated mention vas mrde of 

 the fact that very different kinds of cells, of very different 

 origin, can under certain abnormal conditions assume "foreign" 

 aharacteristics v/hich often v;arrant conclusions as to changes 

 in the physiolobical -effectiveness of cells. Cells, which re- 

 main colorless under normal conditinns, develop chloroplasts. 

 Thin-walled cells obtain, through thickenings of their membrane?, 

 an especial wall structure; for example, a retioxilated one, and 

 so forth, Closer consideration nov proves, that vn abnormal 

 turning green takes place only in plants which even und er near - 

 mal conditions somewhere develop chloroplasts, that, further, 

 abnormal reticulated wall-thickenings occur only in plants, in 

 which the same formative process is known already in certain 

 normal elements, Therefore peculiarities of the cytoplasm con- 

 sidered as pre-requisites for the formation of chlorophyll, 

 certain wall-thickenings, etc, are not prodiiced "anew" under 

 the influence of certain abnormal conditions, b^t only become 

 active in those cells and tisEues in which, in a normal develop- 

 ment the external and internal conditions necessary for chloro- 

 phyll forme-tion are not realized* Among others we must consider 

 the nutritive conditions of the cells; in which, therefore, in 

 other v/ords, the cjrtoplasm for some reason does ndj "make use' 

 of its capacity for developing chloroplasts etc. 



Although the plant, so far as the inner structiare of its 

 cells is concerned, even under abnormal conditions, must manage 

 (291) to live with. the same capabilities that aare also active in nor- 

 mal development, yet all possible heterogeneous kinds of cells 

 may be produced in such a way that the known processes of dif- 

 ferentiation are enacted in the larger or smaller cells, or m 

 those formed otherwise than under normal conditions, I call 

 attention again to the pe>culiar callus hypertrophies of the 

 Orchids (Fig. 26), to the parenchymatic tracheids in' callus 

 tissue (Fig. 67), to branched woody fibres (Fig, 70), to the 

 tracheids which occur at times in prothallia and many others. 



