SPECIES IN AGAVE. 



(Plates XXXII and XXXIII.) 



By WILLIAM TRELEASE. 



{Read April 22, 1910.) 



As Dr. Gray once said, species are nothing but human judg- 

 ments (he even added very fallible judgments as some of us know 

 to our sorrow), and as such they have changed and may be 

 counted on to change with the minds that frame them, oscillating 

 about the truth in a series of approximations to a definition of the 

 also — but less rapidly — changing forms of living nature. A glance 

 at the work of their makers shows that .they have always been 

 obscured by insufficient knowledge of real differentials, and even 

 in the masterly synopses of Linnaeus and other epitomizers too few 

 of them have usually been known to permit characters to be so 

 framed as unquestionably to exclude those to be revealed by the 

 exploration of new regions or by closer study at home. Botanists 

 have rarely been able to build on the work of their predecessors 

 without frequent reference to more than original descriptions, and 

 in their effort to fix types they have been more helped by that unin- 

 spiring accumulation of dried plant remains, the herbarium, than by 

 anything else unless indeed it be a well done illustration showing a 

 pre-specific existence of a species — if such an expression may be 

 used notwithstanding a sometimes handy convention that species are 

 not to be sought earlier than the date of their formal binomial 

 christening by the great Swedish naturalist. 



Succulents have offered rather more than their share of trouble 

 to those who have undertaken to describe and classify them, for one 

 reason because they usually are, or appear to be, difficult of preser- 

 vation in the herbarium. The fallacious notion, that, being easily 

 brought in alive so that they may be grown in gardens, they are 

 more surely preserved in this way for reference, may have had 

 something to do also with damping the ardor of herbarium makers. 



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