BILLINGS: EMBRYO NUTRITION IN LABIATE. 73 



tissue. If the growth had been uniform in all directions the 

 long axes of the haustorium and endosperm tissue would have 

 been approximately parallel. In Phrysostegia the endosperm 

 grows in a one-sided fashion, producing a bend in the embryo 

 sac of about ninety degrees. The haustorium is a club-shaped 

 sac containmg a few large nuclei. Its upper or micropylar end 

 is vacuolated, while its lower end, adjoining the endosperm 

 tissue, is densely protoplasmic. The suspensor is exceedingly 

 long. 



The position of the antipodal canal is peculiar in this species. 

 It is located near the haustorium — a situation explained by the 

 short length of the vascular bundle, as well as the one-sided 

 growth of the endosperm tissue. The constriction existing be- 

 tween the haustorium and endosperm tissue is comparatively 

 wide, with the result that the cytoplasm of the haustorium 

 comes in contact with the endosperm tissue to a greater extent 

 than in any other species examined. 



Leonurus cardiaca. 



Leonurus has a large haustorium with a contour much like 

 that of Stachys (fig. 9) . The haustorial nuclei have a more or 

 less fixed position in that portion lying nearest the endosperm 

 tissue. This is the reverse of the condition in StacJujs, where 

 the nuclei lie in the micropylar region. Their number varies 

 from four to six. The definite position of the haustorial nuclei 

 would suggest the presence of cell walls, but there was no evi- 

 dence of them. 



Leonurus bears a close resemblance to Phrysostegia in the 

 proximity of the antipodal canal to the haustorium. The canal 

 does not appear in the section shown in figure 9, so its position 

 is indicated by the dotted lines. The lower portion of the endo- 

 sperm tissue and its connection with the vascular bundle 

 through the canal is shown in figure 10. 



BruneUa vulgm'is. 



This species possesses a large coenocytic haustorium contain- 

 ing nuclei without definite position. In this respect it is like 

 Lamium. The antipodal haustorial canal becomes laterally 

 placed, but, unlike the two previously described genera, it re- 

 mains near the base of the endosperm tissue. 



The five genera thus far mentioned belong to the tribe 

 Stachydese. No marked variations occur; in fact, they are 



