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. liirsuta, whose range is 
described in the letter to Darwin of December i8i3 above. 
Criticism should at least be as well equipped as the opinion 
criticised. 
Kew : February 19, 1859. 
My dear Harvey,— I am really sorry for your disappoint- 
ment with the lithogi'apher, it is very disheartening, though 
by the way it is I fear only a righteous and well merited 
retribution for your most unjust, ungenerous, ungi'acious, 
and unphilosophical attack on my Cardaminologia. Thw^aites 
makes the Ceylon C. = liirsuta, sua sfonte, without any 
hint from me. He sent it thus named years ago before the 
Enumeration^ 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 TVTetched 
w^eed as I have. I assui'e 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 infalhbihty, but I have a right in 
common with ever}^ man of science that my conclusion be not 
put aside without my evidence being examined. You who 
know Plocamiuin coccineum and Ceramium ruhrum 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, 3f 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 
^ Enumeratio Flantarum Zeylaniae, Thwaites, published 1859-64. 
