73 



Ti/hile'the air lenticels v^ere covered by a cap of dead 

 brown padding cells, Schenck found "that from the subfiierged 

 lenticels a white spongy tissue develops in the form of a 

 thin plate, which might be as thick as 2mm". Schenck col- 

 lected similar observations on Eupatorium cannabinum . Bid ens 

 tripartitus and various other plants. 



The anatomic investigation oi the masses of vihlte- tis- ■ 

 sue presents the same appearance in all cases. The out- 

 growths consist alwa3?-s of homogeneous elements, of round, 

 or elongated, thin-walled, colorless cells, with large in- 

 tercellular spaces, and often, like a kind of star- parenchy- 

 ma cells, are connected with one another by the tips of 

 short projections (compare fig, 17); - in some places they 

 lose all firm connection ?idth each other, an^^ are deposited 

 as isolated elements in porous layers on groups of cells 

 still connected. The individual cells are alwaj^s free from 

 chlorophyll, have a thin ilayer of cytoplasm and a clear, 

 abundant cell-sap, - Schenck knew the anatomical character- 

 istics here listed; they caused him to compare lenticel 

 outgrowths with the "ASrenchyma" found on numerous water- 

 plants, the water lenticels, according to him "represent 

 *o a certaifl. extent, an aerenchymatic formation in isolated 

 places." Gobell, and v. Tubeuf2 consider the outgrowing 

 lenticel tissue as aerenchyma. 



How since this, according to Schenck, "represents a 

 tissue, which suffices for the respiratory requirements of 

 parts of plants remaining under water or in slime, i. e., 

 in media in which the supplying of oxygen must be substan- 

 tially dLifficult in comparison v/ith that for organs found 

 (75) in the air",- since further the observations described lat- 

 ter make it little probable that the lenticels which Schenck 

 ascribed to the aerenchymatic formations of Jussiaea, ITep- 

 tunia, and others, possess this function, we will rather 

 avoid in the following their equalization with the aerenchy- 

 ma and v/ill speak only of tissues resembling aerenchytna. 



Ontogenetic investigations shov; that lenticel-escres- 

 cenees arise from normal lenticels by enlargement of the 

 phelloderm cells, therefore, in their formation, v;e have 

 to deal with hypertrophy. Devaux^ has proven in a few 

 instances that hypertrophy begins in the outer las^-ers of 

 the phelloderm and extends to both of the innermost cell 

 layers. A new meristem is then produced from them. In 

 other cases the cells of all the" phelloderm layers, to- 

 gether with the bark cells lying under the lenticel, hy- 

 pertrophy; the new lenticel-meristem arises then from the 

 more deeply lying layers of the bark tissue. According to 



1. Gobei. Pflanzenbiol. Schilderungen, 1893, p. 261. 



E. V. Tubeuf. Uete, Lenticellenwucherungen (Aerenchyma) 

 an Holzgewachsen. Forstl.-Naturw, Ztschr. , 1896, p. 405. 



3. Rech. s. 1. lenticelles. Ann Sc. Hat. Bot. 8me ser. 

 T. XII, 1900, p. 139. 



