BILLINGS: EMBRYO NUTRITION IN LABIATE. 75 



position of the antipodal canal of previously described species. 

 Its origin may be explained by a growth of the tissue into the 

 canal, which it thus displaces. The haustorium contains but 

 one or two nuclei with no formation of tissue. 



Mentha canadensis. 

 The integument in this species is not extensive, yet there is 

 a large cosnocytic haustorium present which closely resembles 

 that of Pijcnayithemiim. Like Pycnanthemiim, there is in 

 Mentha an early obliteration of the canal connecting hausto- 

 rium and endosperm tissue. Lycopus, on the other hand, rep- 

 resents the other extreme, in which the canal persists for a 

 long time. PycnantheTmim, Lycopus and Mentha belong to the 

 tribe Satureinese. 



Salvia azurea and Salvia lanceolata. 



These two species will be considered together, as they pre- 

 sent many points in common. As compared with the repre- 

 sentatives of other genera, however, they show marked differ- 

 ences. In the first place, they are unique in having two haus- 

 torial outgrowths, one coenocytic and one composed of ordinary 

 endosperm tissue. In addition, there is a well-developed antip- 

 odal canal. 



In order to follow better the development of the haustoria, it 

 will be advantageous to examine the definitive embryo sac and 

 consider some of the phenomena immediately following fertili- 

 zation. The definitive embryo sac of Salvia lanceolata is shown 

 in figure 14. It is short, and in comparison with the extensive 

 integument is relatively insignificant (fig. 15). The shortness 

 is the more noticeable when the amount of space occupied by 

 the egg apparatus is taken mto consideration. The embryo 

 sac is filled with a reticulated cytoplasm, which is distinguished 

 from that of Lamium amplexicaule and other species examined 

 by the absence of vacuoles. The antipodals lie in the depression 

 which marks the beginning of the canal to the vascular bundle. 

 The small size of the embryo sac necessitates the proximity of 

 the endosperm nucleus to the egg apparatus. 



Fertilization is followed by a very slight elongation of the 

 egg cell — a marked variation from the condition found in the 

 species of other genera examined. The explanation for this 

 difference lies in the fact that none of the space occupied by the 

 definitive embryo sac is to be included in haustorium formation, 



