74 KANSAS UNIVERSITY SCIENCE BULLETIN. 



much more nearly alike than they are different. Phrysostegia 

 appears to be the most divergent, but such divergence is really 

 trivial. All are characterized by a large micropylar hausto- 

 rium — a feature, however, which it shares with representa- 

 tives of other tribes. 



Teucrium canadense. 

 A glance at the diagram shown in figure 11 will show the 

 relative position and size of the different portions of the em- 

 bryo sac. The most noticeable difference between this species 

 and those previously described is the relatively small size of the 

 haustorium. The failure of the haustorium to enlarge much 

 is doubtless mainly due to its proxity to the end of the beak-like 

 extremity of the integument. There is but little room for en- 

 largement. The haustorium contains a few nuclei that do not 

 form a tissue. Whether this organ is really functional or not 

 is difficult to determine with certainty. At most its activity 

 can be only very slight, otherwise the extremity of the integu- 

 ment would undergo dissolution. The endosperm nuclei which 

 are found in it do not have the size nor the altered appearance 

 seen so frequently in vigorously acting haustoria. It would ap- 

 pear from this that alteration in the haustorial nuclei is to 

 some extent at least proportional to the activity of the organ 

 to which they belong. 



Pycnanthemum lanceolatum. 

 The general configuration of the embryo sac is much like 

 that of Lamium (fig. 12). The coenocytic haustorium attains 

 a large size, with the result that most of the micropylar por- 

 tion of the integument becomes absorbed. The constriction 

 between haustorium and endosperm tissue is soon obliterated, 

 so that the two lie contiguous over a considerable area. The 

 suspensor is long, as in the previously mentioned species, but 

 owing to the size of the haustorium most of its length is found 

 within the limits of this structure. 



Lycopus rubellus. 

 Lycopus 7^ubellus, when contrasted with Pycnanthemum, 

 which belongs to the same tribe, differs in two respects; the 

 haustorium is small, and the constriction lying between it and 

 the endosperm tissue is relatively long (fig. 13). The basal 

 portion of the endosperm tissue extends in a beak-like process 

 to the end of the vascular bundle. This process occupies the 



