THE EVOLUTION OF PLANTS 



green or chlorophyll. They appear to be algae that have 

 permanently lost this substance, but we do not yet know 

 enough to speak with assurance as to the origin of the fungi. 

 In contemplating this exhibit, or the plant kingdom itself, 

 here represented in miniature or by samples, one is impressed 



STEPS IN THE HISTORY OF 

 PLANT CLASSIFICATION 



ABOUT 300 BC-THEOPHRASTUS: 



TREES, SHRUBS, HALF- SHRUBS & HERBS 



ABOUT 1700- JOHN RAY: . 



HERBS {^S^^l-^^^^ /MONOCOTYLEDONS 



\FLOWERING < DICOTYLEDONS 

 TREES a SHRUBS ^ 



1753- LINNAEUS •• 



BINOMIAL NOMENCLATURE 



1789- L. DE JUSSIEU: 

 AGOTYLEDONS, MONOCOTYLEDONS &DICOTYLED0NS 



ABOUT 1849- HOFMEISTER 



DEMONSTRATED UNITY 

 OF PLANT DEVELOPMENT 

 IMPLYING EVOLUTION 



THE EVOLUTION OF PLANTS 



MONOCOTYLEDONS 



CYCADS 



FERNS 



MOSSES 



FUNGI 



DICOTYLEDONS 



CONIFERS 



HORSETAILS 



CLUBMOSSES 



LIVERWORTS 



ALGAE 



fl -STRUCTURE (MORPHOLOGY) 

 EVIDENCES < 2- DEVELOPMENT (ONTOGENY) 

 (^3- FOSSILS (PALEONTOLOGY) 



Fig. 1. — ^^At the left, a brief outline of the history of plant classi- 

 fication. At the right, a genealogical tree indicating that the modern 

 groups of plants were descended by evolution, not one from the 

 other, but from preexistent ancestors, which were also genetically 

 related. This conclusion is based upon a study of the structure 

 (morphology) of existing plants, the life-histories of individual 

 plants (ontogeny) , and a comparative study of the morphology of 

 fossil plants (palaeontology or palaeobotany) and modern plants 

 (botany). (From the label jorjhe Evolution Group at the Brook- 

 lyn Botanic Garden.) 



by the fact that, amid the endless diversity of plant forms, 

 it is possible to bring order out of apparent chaos. Men 

 have been trying to do this with plants for more than two 

 thousand years. What a long, hard struggle it has been to 

 try to understand Nature! About 300 B.C. Theophrastus, a 



[139] 



