Trelease — Botany During the 19th Century, 129 



distinct group of primary importance in any natural classifica- 

 tion, the researches of Ho fmeister contributing largely to this 

 result; but even to-day, convenience of treatment, if no other 

 reason, causes specialists to write commonly on either algae, 

 fungi or lichens, according to the group of thallophytes they 

 may be studying. And yet the beginning of better things 

 has been made, for DeBary's suggestion and Schwendener's 

 morphological demonstration that lichens are in reality only 

 certain fungi with enslaved or commensal algae as an integral 

 and usually necessary part of their organization marks the 

 close of the third quarter of the century, and in the conclud- 

 ing quarter various efforts have^been made at a classification 

 of the thallophytes on more scientific grounds than the pres- 

 sence or absence in them of chromophyll-bearing cells or tis- 

 sues. Though the goal may not yet have been reached, these 

 efforts are full of promise for success in the century that is 

 now on the calendar. 



EVOLUTION AND CLASSIFICATION. 



It was in the first decade of the century that Lamarck, fol- 

 lowing a line of thought that had caused men long before his 

 time to speculate on the varied forms of nature, attempted 

 to show how environment, use and disuse of parts, and sim- 

 ilar natural factors might have brought about modifications 

 leading to the origin of new species from ancestors otherwise 

 characterized; and the year 1858 will always stand out in 

 prominence in the history of biology because of the simulta- 

 neous presentation in that year of almost identical explana- 

 tions of the manner in which natural selection, or the survival 

 of the fittest in life's struggle, might and of necessity must 

 lead to the repeopling of a given territory by new forms de- 

 scended from those pre-existing, provided, in the progress of 

 time, the conditions of life were changeful and variations 

 were present in oifspring, as compared with one another and 

 their parents, — as was well known to be the case. Darwin 

 and Wallace, the authors of these first papers, did not go to 

 the bottom of their great subject, and the last word on it is 

 far from having been said yet, but the theory of organic 

 evolution may be regarded to-day as an axiom on which most 

 philosophical analyses of biology rest as a footing course. 



