ARRANGEMENT OF STORAGE-CELLS 



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(Fig. 1(J5 b), which is also a transverse section through the embryo, 

 shows that the endosperm-cells are palisade-shaped near the periphery, 

 but rapidly become isodiametric further in. In this case the palisade- 

 like form of the peripheral cells cannot possibly be connected with 

 translocation, but must be a purely mechanical device. For one thing, 

 the radially elongated peripheral elements are those which have the 

 smallest amount of translocation to per- 

 form, whereas the inner part of the 

 endosperm, which should be possessed 

 of the highest conducting capacity, con- 

 sists of isodiametric cells. Further, the 

 presence of numerous pits on the lateral 

 walls of the palisade-shaped peripheral 

 cells suggests that active translocation 

 takes place, during germination, across 

 the long axis of these cells. The outer- 

 most layer of all has no pits on its 

 radial walls, or, at anyrate, very few. 

 This feature likewise represents a 

 mechanical adaptation, being clearly 

 designed to prevent any weakening of the 

 lateral walls in the layer which acts as 

 the special mechanically protective tissue 

 of the seed. 



The four or five outermost layers on 

 either of the flattened sides of the 

 mericarp of Slier trilobum (Fig. 165 a) 

 are palisade-like, whereas the inner por- 

 tion of the endosperm is made up of 

 cells which are either isodiametric or, 

 more frequently, elongated in the tan- 

 gential direction. Since the fairly thick 

 lateral walls of the peripheral cells are 

 quite devoid of pits, there can be little 



doubt that, during the depletion of the endosperm, the mobilised 

 reserve-materials of the outer layers travel, to start with, in the 

 radial direction until they reach the inner region, where they are 

 directed towards the developing embryo. The path followed by the 

 emigrating reserve-materials in this case is, therefore, closely similar 

 to the course pursued by the synthetic products in the case of a 

 leaf which has palisade- tissue on both faces. 19 * 



Hitherto discussion has been confined to tissues containing stores 

 of plastic material which are destined to be utilised by the plant as a 



A. Part of a radial L.S. through the 

 endosperm of Siltr trilobum. B. Peri- 

 pheral portion of a T.S. through the 

 seed of Polvgonatum vulgare. C. One of 

 the thick, stratified walls of an endo- 

 sperm-cell of Fritillaria imperialis, in 

 section ; two pits are shown, x 510. 

 D. Various forms of pits from the endo- 

 sperm of Fritillaria imperialis (semi- 

 diagrammatic). X 500. 



