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it forms only a narrow layer round the endosperm, somewhat 

 thicker near the chalaza (greatest thickness of the embrjosac 1,2 mm., 

 of the nucellns 1,5 mm.). Here also the lower part of the embryosac 

 is not filled, but is entirely abortive. The endosperm-cells are of 

 rather unequal size, most nuclei do not look normal, but still divisional 

 stages occur; in the more peripheral cells small grains which strongly 

 absorb staining substances appear outside the nucleus. As in some 

 other cases, the impression is got here that the formation of the 

 endosperm takes place rather irregularly, as if in various spots within 

 the embryosac pieces of endosperm-tissue would form which grow 

 towards each other so that seemingly moi'e than one endosperm lies 

 in the embryosac. At any rate this seems to be so when one limits 

 his attention to one preparation ; by comparing, however, the different 

 successive sections of one ovule there finally appears to be only one 

 mass of endosperm. The formation of tiie endosperm begins in the 

 lining of the wall of the embryosac and from there proceeds inwardly; 

 in this process the cavity is gradually filled up, the endosperm now 

 meets itself from various sides and it is tiiese divisional lines that 

 remain visible. 



That the formation of an endosperm starts indeed at the periphery 

 of the embryosac, appears e.g. from an ovule, collected on Septem- 

 ber 19. Here tlie size of the whole endosperm is greater than in 

 the already mentioned ovules (diameter 1,35 mm.), so that only a 

 very narrow layer of nucellus-tissue is visible all round, mostly at 

 the chalaza (greatest diameter of the nucellus 1,4 mm.); but the 

 whole endosperm is hollow and in this cavity remnants of the proto- 

 plasm of the embryosac are visible. The endosperm-cells are here 

 of very different sizes and so also the nuclei vary much. Some of 

 them look normal, show karyokinesis, others are enlarged, have 

 assumed all sorts of capricious shapes, the number of nucleoli has 

 greatly increased and a number of fragmentation stages can be observed. 



Two ovules, collected on September 10, show a still further 

 developed endosperm. The nucellus tissue has been more displaced, 

 the shape of the endosperm-cells is pretty regular, their cell-wall 

 is somewhat thickened, the nuclei are almost normal; in any case 

 there is much less indication of fragmentation than with the just 

 mentioned ovule. 



In an ovule, collected on September 19, the endosperm is so 

 strongly developed that of the nucellus tissue hardly anything remains 

 visible. This also applies to the cases which will be described 

 pi'esently. The endosperm-cells have strongly thickened but still 

 fairly gelatinous walls; the contents of the cells consist of a number 



