68 KANSAS UNIVERSITY SCIENCE BULLETIN. 



One of the services that maj' ultimately be performed for 

 taxonomy is that of testing the homogeneity of families. The 

 results could be reached satisfactorily only after all the species 

 of any given family had been examined as to their ontogeny. 

 Taxonomically speaking, the Labiatse are regarded as a fairly 

 homogeneous family with well-marked characteristics. 



Species whose common ancestors are not remote should show 

 similarity in embryonic particulars, since these are doubtless 

 the ones least influenced by environment. 



No attempt was made to work out the stages preceding fer- 

 tilization in every instance. Several species were examined, 

 however, and the series of events constituting the earlier his- 

 tory of embryo-sac development were found to be identical. 



The ovular primordium gives rise to a single megaspore 

 mother cell, from which originates an axial row of four poten- 

 tial megaspores. The most deeply seated of the four develops 

 into the ordinary type of an eight-celled embryo sac. 



The growth of the embryo was followed in detail in Lamium 

 ample xicaule, and it was found that the various stages in de- 

 velopment correspond closely to the plan observed in most 

 dicotyledonous embryos. However, it is not with the develop- 

 ment of the embryo but with the behavior of the embryo sac 

 that this paper has most to do. 



Many of the writings of early investigators who worked along 

 embryological lines show that there was little thought of as- 

 signing physiological significance to peculiar shapes assumed 

 by the embryo sac. More recently quite a number of observ- 

 ers have entered the field, and they have shown the wisdom 

 of correlating morphology and physiology. Bibliographies of 

 their papers have been published from time to time, so that 

 only the literature cited in the text, or very recent papers, will 

 be given here. 



The single and unusually thick integument of many Sym- 

 petalse, including the Labiatse, appear to serve a double func- 

 tion. The outermost layers become transformed into a seed 

 coat, while the inner or remainder, wholly or in part, may be- 

 come a nutritive tissue (Nahrgewebe) which invites, as it 

 seems, the digestive and absorptive activity of the endosperm. 

 Sometimes the nutritive tissue is more or less localized, as can 

 be seen from the deposits of starch in certain regions. In other 

 instances the deposition of food material is general throughout 



