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GARDEN 

 THE TYPICAL SHAPE OF POLYHEDRAL CELLS IN VEGE- 

 TABLE PARENCHYMA AND THE RESTORATION OF 

 THAT SHAPE FOLLOWING CELL DIVISION. 



By Frederic T. Lewis. 



Harvard Medical School, Boston, Mass. 

 Received February 20, 1923. Presented March 14, 1923. 



Free cells of plants and animals can readily be seen from all sides. 

 Though varying greatly in form they are regarded as primarily 

 spherules or globules, easily flattening into discoids, or elongating to 

 form ellipsoids and rods of varying length with rounded ends. But 

 the shape which such cells assume when surrounded and compressed 

 by similar cells, though frequently a subject for inference, has appar- 

 ently never been determined by the observation of actual cells, and 

 on this supposition the present study was undertaken. Even though 

 the examination of many sorts of cells for this purpose is very difficult, 

 and in the most favorable cases is tedious, it seems impossible that 

 such work has not already been done. But if so, it remains unknown 

 to the writer, after some inquiry and a search of the literature at hand. 



Previous publications record and reiterate that the problem of cell- 

 shape is solved in foam. In the earliest observations, Robert Hooke 

 found that within the shaft of a feather the cells form " a kind of solid 

 or hardened froth, or a congeries of very small bubbles," l and 

 Grew described parenchyma as " much the same thing, as to its con- 

 formation, which the froth of beer or eggs is." Two centuries later, 

 Errera remarks that cell-walls " must correspond with such a lamellar 

 system as one gets in pouring soap-suds, beer, etc. from a narrow- 

 necked bottle." Clearly these bubbles are not cubes; and although 

 Grew ascribed cubical cells to the pith of " reed-grass," and at present 

 epithelial cells of a certain type are commonly called "cuboidal," it 

 appears that true cubical cells have never been shown to occur, even 

 as rare exceptions. 



Parenchymal cells which are "pentangular, sexangular, and sep- 

 tangular" were seen by Grew, and the prevailing hexagonal form of 

 such cells in section is shown in some of his figures. Cut tangentially, 

 the cells of cork were found by Hooke to be as regularly hexagonal as 



1 Schwann, in his Mikroskopische Untersuchungen, Heft 1, 1838, p. 94, con- 

 firmed the accuracy of Hooke's comparison of the cells in the pith of a feather 

 crwith those of cork, but without citing the earlier work. 



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