AFFINITIES OF THE GROUPS. 567 



In the second place, many of the so-called species in de- 

 scriptive works are but varieties, while in other cases the 

 same forms have been described under different names. This 

 is true in all the groups of plants, and scarcely a monograph 

 now appears in which there are not cases of the reduction of 

 a supposed species to a synonym or variety. 



606. With these considerations in mind, we may examine 

 the catalogues and make some general estimates. Steudel in 

 1824 catalogued in " Nomenclator Botanicus" 59,684 phan- 

 erogams and 10,965 cryptogams, making a total of 70,649. 

 In the second edition, published in 1841, the number of 

 phanerogams was increased to about 78,000. Lindley, in 

 1845, estimated the number of dicotyledons to be 66,488, the 

 monocotyledons 13,952, and the cryptogams 12,480, making 

 a total of 92,820. De Candolle's " Prodromus," begun in 

 1824 and continued to 1873, contains, according to Alph. De 

 Candolle's historical note in Vol. XVII. of that work, de- 

 scriptions of 58,446 dicotyledons and 429 gymnosperms. 



Duchartre estimates the known species of phanerogams at 

 about 100,000, and of cryptogams at about 25,000, and ven- 

 tures to place the whole number of species in the world at 

 from 150,000 to 200,000. Dr. Gray quotes De Candolle's 

 estimate of the known species of flowering plants, amounting 

 to from 100,000 to 120,000, and says that "the larger num- 

 ber may perhaps include the higher orders of the flowerless 

 series," and in speaking of the lower cryptogams says that at 

 present "no close estimate can be well formed of the actual 

 number of species."* 



607. The Affinities of the Groups of Plants. Many at- 

 tempts have been made to construct diagrammatic figures 

 which should indicate the affinities of the different groups 

 of the vegetable kingdom. While it is impossible to do this 

 with any great degree of accuracy, we may yet show in this 

 way certain relations, more clearly than can be done other- 

 wise. The subjoined diagram may be taken to indicate in a 

 general way the writer's present notion of the affinities (i.e., 



* In his " Botanical Text-Book," 1879, Part I., p. 346, foot-note. 



