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20 years ago, and I began to study them, I was Struck with the cors- 



ness, the want of scientific precision and spirit, with which that 



most interesting fa.mil y has been treated. Even great botanists, like 

 and Martius 



De Candelle have not done them justice; not to say anything cf the mess 

 of dilletanti, who did nore to confound and confuse Science than to 

 felucldate« 



I began ny studies a new, ab ovo f ,based on the immutable principle, 

 that the flower and the f ruitif ication only can leadon, and must lead 

 on, to true scientific results, in that we can study Cactaceae not 

 any better than Oaks or Roses fron the mere organs of vegetationand 

 that we must have the flowerand the fruit of every species t and know 

 them well in all their details, bef ore we can say that we know a spe- 

 cies of Cactus. 



I have been further well aware, that a great many species, comme- 

 morated. in the books and in Garden Cätalogues, are merc. varieties, 

 so that the number of real species must be vastly reduced; but I al- 

 so knowthst only a botanist in loco could discover the true limlts 

 of species; only one who sees a prreat many individuals and studies 

 them can learn to distinguish the essential from. the unesse^tial cha~ 

 racters. I would not consider that I knew a species if I was not well 

 acqu.ain.ted with the flower and fruit, and I would hesitate to say that 

 I knew i t well if I had not seen many specimens, if possible und er 

 differentcircumstances in different localities etc. so that I could 

 judge of the degree and the limit of their variations and separate 

 the constantand essential from the accessory, changeable and unlmpor- 

 tant characters.And such an opportunity I never enjoyed, and such an 

 opportunity do you now have llmprove it by all means- a>-d anything 

 I can do to assist you shall be most faithfully and che erfully done. 



0* course, we have to take into consideration what our prede- 

 cessors have done;but, though frequently they have paved the way for 



