314 HARSHBERGER— TAXONOMIC CHARTS OF THE [April 15 



tables of taxonomic relationships in their large text-book of botany 

 C Cours de Botanique Phanerogames "). 



Bearing upon this same field of botanical speculation and inves- 

 tigation, a number of important papers have appeared which ap- 

 proach the subject from the morphologic and histologic sides. Cur- 

 tis in his ''Text-Book of General Botany" (1897) conjectures the 

 nature of the affinities of monocotyledons and dicotyledons, stating 

 that the monocotyledons may be considered as a branch that has 

 departed from the dicotyledonous type and become structurally 

 weak owing to their aquatic habitat. He also gives a short state- 

 ment of the evolution of the flower and of floral types. One of the 

 most interesting theories regarding the evolution of the higher 

 flowering plants is one proposed by Balfour^ on the philosophy of 

 water and vegetation. In this paper, Balfour traces the evolution 

 of the types which being exposed to the failure of water show con- 

 sequential difficult movement of the sperm cells and, therefore, have 

 adapted themselves gradually to a dry environment by the develop- 

 ment of flowers and true seeds. Campbell- describes the causes 

 that led to the general abandonment of the aquatic habit and the 

 adoption of a land habit, which characterizes the predominant plants 

 of the present time. The adoption of the seed habit, according to 

 Scott,^ gives the plant possessing such a habit the following ad- 

 vantages : 



1. Pollination on the parent plant, and consequently greater cer- 

 tainty in bringing together the two kinds of spores. 



2. Fertilization either on the plant or at least within the sporan- 

 gium giving greater certainty of success and protection at the criti- 

 cal moment. 



3. Protection of the young prothallus from external dangers. 

 Rendle in the New Phytologist (11:66, 1903) considers the 



origin of the perianth in seed plants, and later in 1904 in his book 

 the " Classification of Flowering Plants " traces the affinities of the 



^ Balfour, Prof. I. Bayley, '* Philosophy of Water and Vegetation, 

 Nature, 64: 557, October 3, 1901. 



^Campbell, D. H., "The Origin of Terrestrial Plants," Science, n. s., 



XVII: 93, 1903. 



^ Scott, D. H., "Origin of the Seed Habit," Nature, 68: 377-3^2, 1903. 



