470 ON SPECIES 



His care in working out species detail is illustrated by a 

 friendly scolding of Harvey in 1859 for rejecting on inadequate 

 grounds the identification of an African cress, Cardamine 

 africana, with the widespread C. Mrsuta, whose range is 

 described in the letter to Darwin of December 1843 above. 



Criticism should at least be as well equipped as the opinion 

 criticised. 



[Kew : February 19, 1859. 



MY DEAK HAEVBY, I am really sorry for your disappoint- 

 ment with the lithographer, it is very disheartening, though 

 by the way it is I fear only a righteous and well merited 

 retribution for your most unjust, ungenerous, ungracious, 

 and unphilosophical attack on my Cardaminologia. Thwaites 

 makes the Ceylon C. = hirsuta, sud sponte, uiithout any 

 hint from me. He sent it thus named years ago before the 

 Enumeration a was conceived of ; though I altogether agree 

 with him. 



Who are you ? that you, without seeing my materials, 

 say that africana and hirsuta cannot be the same. You 

 might at least go over my evidence before you condemn. I 

 just wish that you had spent as many hours over the wretched 

 weed as I have. I assure you that when I did the N.Z. 

 Flora I spent several mornings at that plant alone, and had 

 spent a long time at it when I did the Antarctic, and have 

 since on doing the Indian plants ; always with the same 

 result. I do not demand infallibility, but I have a right in 

 common with every man of science that my conclusion be not 

 put aside without my evidence being examined. You who 

 know Plocamium coccineum and Ceramium rubrum might 

 be careful I think of Cardamine hirsuta in another man's 

 books ! Scolding apart, my belief is that C.h. is one of those 

 plants of which you may make 20 species or one, if you 

 make 2 you must make many more, and seeing that C. 

 africana is in my apprehension joined to hirsuta by inter- 

 mediate forms of habit, of foliage, of inflorescence, and of 

 pod, it ranks according to my philosophy as a variety and 

 not as a species. As soon as geological or other causes have 

 destroyed said intermediates then I will make it a species. 

 If each Botanist is to insist on keeping two dissimilar things 



1 Enumeratio Plantarum Zeylaniae, Thwaites, published 1859-64. 



