MICHIGAN ACADEMY OF SCIENCE. 143 



can be mat died within the Dieotyledoneae themselves, e. g. single 

 cotyledon, scattered vascular bundles, of the ''closed" type; trime- 

 rous flowers; parallel veins, etc., so that it would seem a not well 

 grounded assumption to base a separate origin of the two groups 

 upon these minor differences when so many of the more important 

 characters are identical in both groups. 



These facts have led botanists in recent years to seek for a group 

 or groups of ])lants that might represent transitional forms from 

 one class to the other. Some have sought to derive both groups 

 independently from a hypothetical ancestral complex of true flower- 

 ing plants from which have emerged on one hand the ^lonocoty- 

 ledoneae, and on the other, the Dieotyledoneae; others have sought 

 to derive the latter from the former or vice versa. Under the in- 

 fluence of Eichler, whose system was adopted in the main by Engler 

 and I'rantl' the primitive Monocotyledoneae as well as Dieotyle- 

 doneae were looked upon as being those forms whose mostly di- 

 clinous flowers were simple in structure and without a perianth. 

 From these (respectively Typhaceae and Piperaceae) we find a 

 gradual development to plants with more and more complete flowers. 

 by the develo]»ment of at first one, finally two series'; of perianth 

 members, the attainment of hermaphroditism, the increase in num- 

 bers (if the various floral parts and their subsequent gradual re- 

 duction and union until the Orchids in the Monocotyledoneae and 

 the Composites in the Dieotyledoneae marked the respeective 

 culminations of the two groups. This scheme of classification has 

 several very serious defects. Thus we should expect to find the 

 first, supposedly simplest, ]\[onocotyledoneae and Dieotyledoneae to 

 show the most numerous points of similarity, with greater and 

 greater dissimilarity coming in as we progress further up each 

 series. This is, however, far from being the case. Then, again, 

 this scheme requires the independent development, in both classes, 

 of flower types and structures that have very many points in com- 

 mon and that have rather a wide distribution in each class. I refer 

 particularly to the pentacyclic type of flower and to the calyx and 

 corolla as well as to flowers with numerous separate carpels, all 

 of these being characters that would much better be looked upon 

 as showing a common origin than as having developed independent- 

 ly in two distinct evolutionary lines. Other points might be 

 brought forward but these will suffice. 



O. E. Bessey proposed in 1803^ after having taught it for many 

 years previously, a scheme of classification in which a common 



5. Engler. A. und Prantl. K. Dip natiirliohen Pflanzonfainilien. 1SS9-1914. 

 G. Bessey. C. E. Evolution and Classification, 1893. 



