239 



Some oases will be discussed later, In which the eotion 

 of nutritive and poisonous substances and their trophic and tox- 

 ic effects ulll be illustrated. As said above, in many cases it 

 must remain undecided for the present in trophic action, v/hether 

 a freeing or a preparatory'' influence of the living cells and 

 tissues is involved here. 



Trophic effoots . varjT'ing from the normal are produced in 

 various v/ays,- an insufficient supply of nutritive substances 

 onuses hypoplasia, v/hile an over abundant one leads to hyper- 

 trophy or hyperplasia/ 



An hypoplastic formation ht cells and tissues always occurs 

 when insufficient amounts of nutritive substances lie nt the 

 disposal of the organisms or of its spparate parts,- or the con- 

 position of the food stuffs offered does not supp"4.y the sub- 

 stances required for a normal deve^-opment/ We observed hypo- 

 plasia in plants which live in the dark or in places free fro© 

 caiBbon dioxiff, which therefore by assimilation can not produce 

 from thdmselvss the necessary amount of nutritive substances; 

 further!^ in tho;3i» plants, in vthich transpiration is arrested by 

 cultivation under water or in moist plaices as v;ell as by the 

 exclusion of ligljt, and whose transpiratory current is therefore 

 too weak to supply the needed amount of nutritive substances 

 to the different parts of the organism. "Shade -leaves" are also 

 to be considered in this connection. It must remain doubtful 

 whether in the production of galls bearing the character of hy- 

 poplasias, the giving up of nutritive material to the parasite 

 which produces the gall may play tlie chief part or not, W© can 

 further observe hjnpoplasia in plants, which must support their 

 existence without iron; calcium or other "indispensable" sub- 

 stances, The conditions in the homoeoplastic excrescences of the 

 sugar beet already described (p, 139) are more complicated. 

 Uefli formations are produced, which apparently use up all the 

 available amounts of nutritive substances, so that the neighbor- 

 ing tissues seem to be arrested developmentally. The "struggle 

 of the parts of the organism" leads here to a "correlation 

 hyperplasia"-*-. 



A continuance of the processes of growth and differentiation 

 is produced by trophic influences when the cells are brought, by 

 some meqns, to the production of substances Vvlthout r/hich cer- 

 (280) tain processes can not take place. The formation of chlorophyll 

 is clearly dependent on some unknown substances, which in most 

 plants are produced in the cells themselves only under the influ- 

 ence of light. Many algae, however, are known to form chlorophyll 

 in the dgrk, aftsr having been supplied with organic nutriment 

 and it seems not at all impossible that future investigations 



•'• At times, in the formation of "semi"-annual rings, we 

 have to do with the same phenomenon (p, 25), Further in the ob- 

 servations of Elfying (loc, cit.) v/ho found in bent inflorescence^ 

 stalks that the eollenchyma was formed abnormally abundantly on 

 the convex side, but was retarded on the concave side. Still, 

 it is undeniable that in the fiast named case, still other con- 

 structions are obvious. I fefer further to that said above 

 (p. 140) for Aristolochia-ridges (Observations by Magnus).- If 

 in Erineum galls, the epidermal cells hypertrophy greatly, but 

 the parts of the mesophyll belonging to them, seem arrested in 

 their development (fig. 38), a correlation-hypoplasia may possi- 

 bly be present; the arrestment, however, can also illustrate the 

 effect of gall-poison. 



