642 POPULAR SCIENCE MONTHLY. 



hothouse flowers and also by dried specimens, of which one hundred 

 kinds were given to each teacher. This course was given to teach- 

 ers, many of whom could by means of a key analyze any common 

 flower, but who knew nothing of the principles of plant relationship. 

 The theories of special creation and of evolution were explained, 

 and the theory of descent with variation was taken as a hypothesis. 



Starting with this theory of evolution as a basis, the structure 

 of certain families was studied and they were taken as types with 

 which other related families were compared. After a classification 

 of all known flowering plants into gymnosperms and angiosperms, 

 and subdividing the latter into monocotyledons and dicotyledons, 

 the lily family was considered as typical of monocotyledons. It and 

 its related families afforded a simple means of demonstrating the 

 problems under consideration. Members of this family were found 

 to be characterized by having an endogenous stem, usually parallel 

 veined leaves, six-parted perianth free from a three-celled superior 

 ovary, and six stamens. The allied families were shown to agree 

 with the type in the internal or fundamental characters, such as the 

 number of carpels and cells of the ovary, but were found to differ 

 in the more external or environmental characters, such as the ar- 

 rangement of the parts of the perianth. 



After studying the relations betw r een the various groups of en- 

 dogens, the trees and weeds of the apetalous division of exogens 

 were next considered, and through Ranunculacece connected with 

 polypetalous dicotyledons. These latter were classified according to 

 whether the parts of the flower were hypogenous, perigynous, or 

 epigynous. These terms signify, respectively, under the pistil, 

 around the pistil, and on the pistil. In this group the rose family 

 presented several modifications of the pistil, according to which it 

 was divided into tribes. 



When the group of Gamopetalw was studied, Solanacece, the 

 nightshade family, with its regular flower, and Labiates, or mint 

 family, with irregular flower, were taken as types with superior 

 ovaries. Various modifications from these types were found in 

 several families. 



Ericacece, the heath family, presented, in its suborders of Eri- 

 cinece, Pyrolece, and Monotropece, which had superior ovaries, and 

 Vaccinice, which had inferior ovaries, an intermediate order be- 

 tween the preceding superce and following inferce, of which latter 

 group Campanulacece was considered a type. 



The relations between many families were traced, and the Com- 

 positce were lastly considered, this family showing the greatest dif- 

 ferentiation with its coalescence of circles, adnation of different cir- 

 cles, reduction in parts, and number of individuals brought together. 



