BILLINGS: EMBRYO NUTRITION IN LABIATvE. 69 



the integument, so that no special part would be likely to be- 

 come a particular point of attack by the endosperm. 



When the absorptive activity of the endosperm is largely 

 centered in some outgrowth or differentiated portion of the 

 embryo sac, the term "haustorium" is applied to such a por- 

 tion. In instances where haustoria are not developed, the di- 

 gestive and absorptive power is more or less equally distrib- 

 uted over the entire surface of the embryo sac. Where ab- 

 sorption is going on most rapidly, the cells directly concerned 

 in the appropriation of the nutritive material are usually, 

 abundantly supplied with plasmatic contents. In case of the 

 presence of a haustorium the endosperm cells lying adjacent 

 to the base of the haustorium show the greatest richness in 

 plasmatic contents. 



The following genera and species of Labiatae form the bases 

 of the detailed description : 



Lamium ampleodcaule. Mentha canadensis. 



Stachys palustris. Salvia lanceolata. 



Phrysostegia virgirliana. Salvia azurea. 



Leonwus cardiaca. Monarda fistulosa. 



Brunella vulgaris. Nepeta catar'ia. 



Teucrium canadense. Dracocephalum sp. 



Pycnanthemum lanceolatum. Scutellaria parvula, 



Lycopus rubeUus. 



Lamium amplexicavle. 

 This species will be given more detailed consideration than 

 the others, for it will serve in a measure as a type of the fam- 

 ily and also as a basis of comparison for the other species. 

 The embryo sac, at the time fertilization is accomplished, con- 

 tains the usual form of Qg^ apparatus (fig. 1) . The endosperm 

 nucleus is large, spherical in form, and contains a vesicular 

 nucleolus. The nucleus does not lie near the egg apparatus, 

 as is the case in so many plants, but at the opposite end of the 

 sac near the disintegrating antipodals. The contour of the sac 

 shows a constriction which may be used to distinguish a larger 

 upper, or micropylar portion, in which the e^g apparatus lies, 

 from a smaller, lower, or antipodal portion, in which the endo- 

 sperm nucleus lies. The endosperm nucleus does not leave the 

 antipodal region, but immediately after fertilization develops 

 a tissue in its end of the sac. Double fertilization probably 

 occurs, though it was not observed. 



