72 KANSAS UNIVERSITY SCIENCE BULLETIN. 



endosperm tissue and a consequent encroachment upon the 

 haustoria. Just when the micropylar haustorium ceases to 

 function is hard to say. Its activity probably does not cease 

 as soon as it begins to be encroached upon by the endosperm 

 tissue. The nuclei in fact remain till late stages in seed de- 

 velopment. 



Stachys palutris. 



The embryo sac seen in figure 7 presents markedly differen- 

 tiated portions. The stage shown here is reached in the same 

 manner as a corresponding one in Lamium. While the endo- 

 sperm is beginning its formation in the antipodal end of the 

 sac a number of nuclei migrate into the haustorium. They 

 distribute themselves over the micropylar end of the hausto- 

 rium, where the cytoplasm is chiefly located. The opposite end 

 is distinctly vacuolated. It will be noticed that the constric- 

 tion is very narrow. Through it passes the suspensor with an 

 enveloping layer of cytoplasm. The regions adjacent on each 

 side of the constriction are stored with starch, the result evi- 

 dently of the absorptive activity of the haustorium. As in 

 Lamium, the cells of the endosperm tissue nearest the hausto- 

 rium are richer in plasmatic contents than those at a distance. 



The canal that conducts from the terminus of the vascular 

 bundle is comparatively long in Stachys. It is sharply bent 

 about midway in its course, one arm running longitudinally to 

 connect with the end of the vascular bundle. 



Stachys and Lamium vary in the structure of their embryo 

 sacs only in minor details, the main difference being the more 

 definitely placed haustorial nuclei in Stachys. The embryo is 

 nourished in both by the endosperm tissue surrounding it, this 

 in turn being assisted in its growth by the activity of the 

 haustorium. It is probable that the suspensor does not func- 

 tion in the conduction of materials to the embryo, on account 

 of the disorganized condition of its cells. The food materials 

 gathered by the haustorium are transmitted to the endosperm 

 tissue through that part of the constriction lying around the 

 suspensor. 



Phrysostegia virginica. 



This species has a peculiar appearing embryo sac when the 

 stage shown in figure 8 is reached. Such difference as may be 

 noted, when it is compared with Lamium and Stachys, is due 

 principally to the direction of growth taken by the endosperm 



