70 KANSAS UNIVERSITY SCIENCE BULLETIN. 



The egg responds to fertilization by elongating greatly, and 

 pushing down into the forming endosperm tissue (figs. 2, 

 3). The elongation is at first due to the growth of the en- 

 tire egg cell. A transverse wall soon separates the suspensor 

 from the proembiyo. It is thus seen that the cell which is to 

 develop into the embryo is removed altogether from the mi- 

 cropylar portion of the sac. For a time this portion contains 

 no active nuclei, the synergids being in a process of disintegra- 

 tion. But endosperm nuclei soon migrate into it through the 

 space lying between the suspensor and the wall of the embryo 

 sac. The nuclei are but few in number and they do not form, 

 tissue (fig. 4). From this time on, the two extremities of the 

 embryo sac are very sharply distinguished. The antipodal end 

 is soon filled with a compact growing tissue that surrounds 

 the embryo. Increase in size of the tissue takes place rapidly, 

 so that the micropylar portion shortly becomes the smaller 

 (fig. 4). A remnant of nucellus can usually be seen as a dis- 

 organized mass of cells lying at one side of the micropylar ex- 

 pansion of the sac. For a considerable length of time the endo- 

 sperm tissue extends only to the constriction, beyond which lies 

 the micropylar region Mdth its wandering endosperm nuclei. 

 An examination of the integument cells surrounding this region 

 shows that dissolution is in progress — due, of course, to the 

 predatory activity of this part of the sac. The antipodal por- 

 tion, with its endosperm tissue, exerts a similar absorptive 

 influence, but the material absorbed by the latter is retained or 

 used up in building more tissue, while that absorbed by the 

 former is not, but is transferred to the endosperm tissue. The 

 micropylar portion of the embryo sac may therefore be re- 

 garded as a haustorium. Evidence of the results of haustorial 

 activity is seen in the unusual richness of plasmatic contents 

 in the endosperm cells bordering on the haustorium. The pres- 

 ence of starch in the basal portion points to the same conclu- 

 sion. 



The nuclei of the haustorium do not form tissue, as has al- 

 ready been stated. In Lamium ample xicaule they take no 

 definite position. Although they have the same origin as the 

 nuclei of the endosperm tissue they differ considerably from 

 them. The chief difference lies in their much greater size. 

 These may attain a length of over thirty micromillimeters. 

 which is greater than the average diameter of an endosperm 



