228 



sure to be observed if it were there, but also in this case 

 no trace of it can be found. So we arrive at the conclusion 

 that hère an endosperm has been formed witliout the 

 embryo having developed. 



An ovule, collected on August 15, shows the smallest 

 quantity of endosperm (fig. 6). The upper part (Vs to %) 

 of the embryosac is filled up with it. The shape of the 

 embryosac has been changed; it is swollen, has become 

 cylindrical or somewhat broader towards the bottom, has 

 a thickness of 0,4 mm., while the nucellus has a maximum 

 diameter of 1,0 mm. The lower part of the embryosac in 

 which no endosperm is found, has entirely collapsed and 

 has evidently been squeezed by the surrounding cells. This 

 same shape of the embryosac was met with only once 

 without an endosperm having been formed in it, namely 

 in an ovule, collected on the same day. In the lining 

 protoplasmatic layer no nuclei could be seen, but still we 

 oelieve that this was a first beginning of the formation 

 of an endosperm. Now the endosperm of the just-mentioned 

 ovule consists of thin-walled cells of varying size;n(U-mal 

 nuclear divisions occur but also nuclei of abnormal size 

 with a number of nucleoli, indicating fragmentation. At 

 one of the sides of the embryosac the formation of the 

 endosperm has not yet been completed. 



Curiously enough the next stage in the development of 

 the endosperm was observed with an ovule, fixed on De- 

 cember 15 (fig. 7). Hère the greater part of the tissue of 

 the nucellus has been displaced, so that it forms only a 

 narrow layer round the endosperm, somewhat thickernear 

 the chalaza (greatest thickness of the embryosac 1, 2 mm., 

 of the nucellus 1,5 mm.). Hère also the lower part of the 

 embryosac is not filled, but is entirely abortive. The en- 

 dosperm-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 



