59 



potassium sulphid, potassium phosphid) carried with it the same 

 phenomena^ of disease, in leaves and internodes an abnormal in- 

 crease of the starch content made itself felt, at least tempor- 

 arily^, Nobba observed similar phenomena in buckwheat plants, 

 (61) which had been robbed of their blossoms^. Schimper obtained 



the same acottoulation of starch In leaves of Trade scantiaSelloi , 

 cultivated in nutrient solutions free from calcium. In all 

 these and similar cases the cells are clearly unable even to 

 develop the diastatic ferments necessary for the solution of 

 starch. 



Similar ohangesr in the cell character will possibly be 

 produced also by abnormal deposits of crystals } however, oases 

 of this kind are as yet unknown to us. 



2. CEIL MEMBRAHE 



Metaplasia of the cells csn be produced by changes in the 

 cell wall, only in so far as the membrane influences the quali- 

 ties of the cell by abnormal growth in thickness or by changes 

 of Its chemical character. 



In the case of growth in thickness of the membrane , two kinds 

 of thickenings should be distinguished: either the protoplasmic 

 membrane forms characteristic thickenings of the wall by the reg- 

 ular formation and distribution of bordered pits, or an irregular 

 deposit of cellulose is laid down here and there on the normal 

 cell membrane, sometimes abundantly, sometimes sparsely, causing 

 the production of massive lumps, or of delicate protuberances, 

 or the like. In metaplastic changes of cell character, wall 

 thickenings of the first kind are very rare; as yet, I know of 

 them only in one single plant family. The second kind of cellu- 

 lose deposit, which never makes any regular recognizable distri- 

 bution of the newly produced material and is distinguished by an 

 absence of bordered pits , occurs more abundantly- To be sure 

 there exists one case in which it cannot be decided definitely 

 whether a degenerative process is present or not,. 



Regular wall-thickenings and also the foi-mation oj bordered 

 pitt? were observed by v. Bretfeld in different orchids , ^'Jo^e 

 leaves were scarred, after injury, by the formation of "netted 

 duct" cells. la leaves of Cvm bidlum alcifol ium, C. ensifolium, 

 Laelia ancei 



gramini folia , lyiaxiiiaria paiiiaiiiora ana m. <^iiiaoj--L^^^^, - 

 '^layer consisting of one or more cell-layers" is conspicuous be- 

 low the destroyed cells and is distinguished from common mesophyll 

 by a massive thickening of the cell walls. These are not thicken- 

 ed uniformly, but contain spores of different sizes, delicately 

 circumscribed, which taken together give the appearance of retic- 

 ulafed walls. The same loells occur in the orchid leaf near the 

 vascular bundle. During the thickening of the cell walls, the 

 cytoplasmic contents of the cell, - the chlorophyll and starch 



^ Hobbe^ Schroder and Erdmann. Ueb. d, organische I-^istung 

 des K. In d. Pfl. Landw. Versuchsstat. , Bd. XIII, p. 321, 386 tt. 

 Compare besides Prank and Sorauer (quoted p. 91, Note 5). 



^ Kobbe. Landwirtsch, Versuchsstat., 1865, Bd. VII, p. 385 



and Bd. ZIII, p. 390. 



II 



3 Zur Frage d. Assimilation d. Mineralsalze durch d, grune 

 Pfl. Flera, 1889, Bd. IXXIII, p« 20V. 



4 Ueb. Vernarbung und Blattfall. Pringsheim's Jahrb. f. 

 wiss. Bot., 1879, Bd, XII, p. 133. 



