238 



to Araceae, a view adopted by Lotsy. The Bentham-Hooker 

 sequence is (i) dicotyledons, (2) gymnosperms, (3) monocoty- 

 ledons; Engler's is (i) gymnosperms, (2) monocotyledons, (3) di- 

 cotyledons, while the right sequence appears now to be (i) 

 gymnosperms, (2) dicotyledons, (3) monocotyledons. 



This evidence has stimulated search for primitive angiosperms 

 among the dicotyledons. According to one view, dicotyledons 

 have arisen by the way of Gnetales to- catkin-bearing trees, such 

 as oak, the early dicotyledons being wind-pollinated, like the 

 conifers. According to another view, forms like the fossil Ben- 

 nettites gave rise to trees like magnolia; on this view the beginning 

 of angiospermy is a response to insect pollination. It is not 

 impossible that both of these lines may have been followed, in 

 which case dicotyledons as a natural group would disappear. 

 Herbaceous plants appear to have been derived from woody, 

 ancestors, following the coming of distinct seasonal changes on 

 the earth. 



The group Sympetalae seems likely later to be broken up to 

 connect with various lower groups, some of the possible lines of 

 connection being Caryophyllaceae — Gentianaceae, Cornaceae — 

 Caprifoliaceae, Passifloraceae — Cucurbitaceae. 



A general appearance of the great tree of plant evolution is 

 thus gradually taking form, strongly supported in the case of 

 vascular plants from fossil evidence-. "The reconstruction of 

 the pedigree of the vegetable kingdom," says Scott, "is a pious 

 desire, which will certainly not be realized in our time." 



Meanwhile must the confusion from an increasing multiplicity 

 of systems in the various countries continue indefinitely? A 

 complete natural system may indeed be distant, but for the 

 progress of science, as well as for practical purposes, some degree 

 of international uniformity is greatly to be desired. 



. References 



Theophrastus. Enquiry into Plants. Transl. by Sir Arthur Hort, London, 1914. 



Greene, E. L. Landmarks of Botanical History prior to 1562. Washington, 1909. 



Meyer, E. H. F. Gcschichte der Botanik. Konigsberg, 1854-56. 



Arber, Agnes. Herbals, their Origin and Evolution 1470-1670. Cambridge, 1912. 



Sachs, J. von. History of Botany 1530-1860. Oxford, 1890. 



Miall, L. C. The Early Naturalists 1530-1789. London, 1912. 



