PATHOLOGIC PLANT ANATOMY 363 



The excessive formation of starch in the leaves of such plants as the 

 buckwheat, Polygonum fagopyrum, when insufficiently supplied with 

 chlorine is a case in point, as also the unfavorable nutrition occasioned 

 by potassium salts, while Schimper succeeded in getting the same ac- 

 cumulation of starch in unusual amounts in the leaves of Tradescantia 

 selloi by cultivation in nutrient solutions free from calcium. 



Cell Membranes. — The metaplastic modifications of cell walls may 

 be considered under two heads. The first condition is found where 

 bordered pits are formed, as in such orchids as Cymbidium ensifolium, 

 LcBlia anceps and Epidendrum ciliare, whose leaves have been scarred. 

 The second modification is seen where the cell walls have been thick- 

 ened abnormally by cellulose knobs, or thickenings. Such cellulose 

 deposits occur about calcium oxalate crystals, oil drops, as in Piper- 

 ace^, Laurace^ and about the hyphae of fungi which penetrate cells, 

 the hyphae along with certain cytoplasmic inclusions being surrounded 

 by the cellulose sheath bridging the space of the cell. Wortmann has 

 found heavy wall thickenings in the epidermis and bark of beans and 

 other twining plants, if they are prevented from carrying out their 

 reaction curvatures, while Kiister noticed the lignification of the cell 

 walls in the leaves of Juglans under the influence of certain plant lice. 



