Septembbk 28, 1900.] 



SCIENCE. 



461 



Adding tliese totals together — 



Phanerogams 105,231 



Pteridophyta 3,452 



Bryophyta 7,650 



Thallophyta • 59,263 



we have a grand total of 175,596 



as the approximate number of recognized 

 species of living plants. 



These figures are sufficiently accurate to 

 show how vast have been the additions to 

 the knowledge of plants in the period under 

 consideration, and they afford much food 

 for thought. In the first place, they indi- 

 cate how closely connected has been the 

 growth of this branch of Botany with the 

 exploration and opening-up of new coun- 

 tries which has been so characteristic a 

 feature of the century. Again, no one can 

 consider these figures without being struck 

 by the disparity in the numbers of species 

 included in the different groups ; a most 

 interesting topic, which cannot, however, 

 be entered upon here. It must suffice to 

 point out in a general way that the smaller 

 groups represent families of plants which 

 attained their numerical zenith in long past 

 geological periods, and are now decadent, 

 whilst the existing flora of the world is 

 characterized by the preponderating An- 

 giosperms and Fungi. 



"We may venture to cast a forward glance 

 upon the possible future development of the 

 knowledge of species. Various partial es- 

 timates have been made as to the probable 

 number of existing species of this or that 

 group, but the only comprehensive estimate 

 with which I am acquainted is that of Pro- 

 fessor Saccardo (1892). He begins with 

 a somewhat startling calculation to the ef- 

 fect that there are at least 250,000 existing 

 species of Fungi alone, and he goes on to 

 suggest that probably the number of species 

 belonging to the various other groups would 

 amount to 150,000 ; hence the total number 

 of species now living is to be estimated at 

 over 400,000. On the basis of this estimate 



it appears that we have not yet made the 

 acquaintance of half the contemporary spe- 

 cies ; so that there remains plenty of oc- 

 cupation for systematic and descriptive 

 botanists, especially in the department of 

 Fungology. It is also rather alarming, in 

 view of the predatory instincts of so many 

 of the Fungi, to learn that they constitute 

 so decided a majority of the whole vegetable 

 kingdom. 



In spite of the great increase in the num- 

 ber of known species, it cannot be said that 

 any essentially new type of plant has been 

 discovered during the century. So far as 

 the bounds of the vegetable kingdom have 

 been extended at all, it has been by the an- 

 nexation of groups hitherto regarded as 

 within the sphere of influence of the zoolo- 

 gists. The most notable instance of this 

 has occurred in the case of the Bacteria, or 

 Schizomycetes, as Naegeli termed them. 

 These organisms, discovered by Leeuwen- 

 hoek 200 years ago, had always been re- 

 garded as infusorian animals until, in 1853, 

 Cohn recognized their vegetable nature and 

 their affinity with the Fungi. These plants 

 have acquired special importance, partly on 

 account of the controversy which arose as 

 to their supposed spontaneous generation, 

 but more especially on account of their re- 

 markable zymogenic and pathogenic prop- 

 erties, so that bacteriology has become one 

 of the new sciences of the century. 



CLASSIFICATION. 



Having gained some idea of the number 

 of species which have been recognized and 

 described during the century, the next point 

 for consideration is the progress made in 

 the attempt to reduce this mass of material 

 to such order that it can be intelligently ap- 

 prehended; in a word, to convert a mass of 

 facts into a science ; ' Filum ariadneum 

 Botanices est systema, sine quo chaos est 

 Res Herbaria ' (Linnfeus). 



The classification of plants is a problem 



