CHAPTER XIX 



THE CLASSIFICATION OF PLANTS 



Natural System. The natural system of botanical classifi- 

 cation is based on the resemblances and differences in plants, on 

 the structure, in fact, of both their vegetative and reproductive 

 organs. The whole plant kingdom can be divided into two 

 sub-kingdoms (i) Phanerogams, and (ii) Cryptogams. All 

 plants belonging to the former division produce flowers and 

 seeds, while those of the latter produce neither flowers nor 

 seeds. The Phanerogams are again divided into (a) Angio- 

 sperms and (b) Gymnosperms. The Angiosperms have 

 their ovules enclosed in an ovary, but the Gymnosperms have 

 naked ovules. The Angiosperms include two main classes (a) 

 Dicotyledons, and (fy Monocotyledons. 



Dicotyledonous plants have the 

 following characters : 



The seedling possesses two seed 

 leaves or cotyledons. 



The foliage leaves are reticulate- 

 veined. 



The vascular bundles are open 

 and arranged to form a circle. 



The parts of the flowers occur 

 either \r\fives, fours, or multiples 

 of these numbers. 



Monocotyledonous plants have 

 the following characters : 



The seedling possesses but one 

 seed leaf or cotyledon. 



The foliage leaves are parallel- 

 veined. 



The vascular bundles are closed 

 and scattered. 



The parts of the flowers are in 

 threes, or multiples of this number. 



Divisions of Dicotyledons. The dicotyledonous plants 

 can be arranged into four sub-classes, according to the structure 

 and arrangement of their floral whorls. 



i. Thalamiflorse. All dicotyledonous plants which have 

 the stamens hypogynous (p, 185), and the pistil superior (p. 183). 



