vo 



Tlje slight differentiation of tissues of etiolated plants 

 has been discussed above; their abnormally elongated organs 

 give rise to new questions. 



We have spoken already of Amelung^s statements concern- 

 ing "medium cell sizBs", Since it v/as determined that organs 

 abnormally undeveloped in size are composed, in part at 

 least, of abnormally small cells, the supposition is obvious 

 that abnormally large organs are composed of especially large 

 cells. We will test this question on the elongated internodes 

 of etiolated plants. 



Highly elongated internodes, petioles, etc., consist 

 -often if not always «- of a greater number of cells than 

 corresponding normal organs. This kind of increase of the 

 cell-number is, hovrever, in itself of no consequence for our 

 consideration, since cell increase alone does not necessitate 

 any change in structural form, (Compa Te Chapter V.) Of more 

 importance to us is the fact, that the abnormally elongated 

 internodes are composed of larger, longer cells, than the in- 

 ternodes of specimens of a normal growth. G3iough the abnor- 

 mal size of the cells, the structural form shown in longitud- 

 inal sections, becomes essentially different from the normal. 

 In measurements of etiolated peduncles of I'ulipa Gesneriana , 

 I found the cells of the ground tissue from a third to indeed 

 a half longer than in the normal ones; in especially highly 

 elongated peduncles tha cells actually became on the average 

 almost twice as long as under normal conditions. I found the 

 same proportions in the elongated organs of other etiolated 

 plant s,+ 



(73) Of course the same is true also of plants which make an 

 abnormal growth in moist places. According to measurements 

 by Stapf^ , who cultivated potato plants under different con- 

 ditions , the length of the pedunelais epidermal cells in the 

 forms making an abnormal growth (cellar go rms) and in normal 

 examples bore a proportion of 217 : 117 , the diameter had in- 

 creased only a little. 3?he guard cells too became larger, 

 they twist more and more strongly ajid at times continue their 

 growth so far that their ends touch (compare fig. 16), and the 

 stoma now has two separate openings. According to Brenner^, 

 in normal examples of S e dum dandr o ideum . in cross«-sections of 

 the leaf , the dimensions of the epidermial cells bear the 

 proportion of 18 ; 8, in specimens making an abnormal growth, 

 of 27 : 12: on the surface section of 11 :4.5 and 13 :7.5 re- 

 spectively, etc. In Crassula partulacea . Mesembryanthemum 



1, Compare also Koch, Abnorme Abanderungen wachsender Pflan- 

 zenofgane durch Beschattung. Berlin 1873 (Bot, Jahresber., 

 1875, Bd. I, p. 283) and others. 



2, Beitr. z. Kenntn. d. Einfl. geanderter Vegetationsbeding- 

 tmgen aul die Formbildung d. Pflanzenorgane u, s. w. Verh. 

 Zool.- Bot, Ges. Wien, 1878, Bd. XXVIII, p. S31. 



3, Unters. an einigen P6ttpfl. Flora, 1900, Bd. LXXXVII, 

 p. 387. Compare also Kohl, Transpiration d. Pfl. u, ihre 

 Einwirkung auf d. Ausbildung Pflanzl. Gew. Braunschweig, 1886. 



