88 ALDRIDGE ON POLLEN. 



fertilization^ it seems to me better to call this by the same name 

 than to invent for it another appellation, inasmuch as I can dis- 

 tinguish the one as an artificial, the other as a natural tube.' 

 I have in this quotation compared tlie operation of an acid 

 and the stigma, for the purpose of clearly explaining the sup- 

 position therein expressed — namely, that the natural tube is, 

 as I have always considered it, a continuation of the inner 

 membrane, produced by the prolonged growth of the inner 

 mass of the pollen, according as nourishment was supplied, 

 an hypothesis in which I already participated, and I there- 

 fore took care to employ expressions, which might convey 

 the idea that this tube lengthened itself at the expense of the 

 fluidity of the stigma." 



The above quotation renders it evident, that Fritzche was 

 not aware of the constant acidity of the stigma, nor of the 

 power which its acid secretion possesses, of causing the de- 

 hiscence of the pollen grains. I might here recapitulate the 

 arguments which I have used elsewhere, in advocacy of the 

 opinion that the boyau is not a tube, but a coagulated heteroge- 

 neous thread. Fritzche, it appears, maintains a contrary opi- 

 nion, and it is my present object, not to prove the correctness 

 of my own views, but to show that they differ from his. This 

 observer first published the fact, which I had independently 

 discovered in 1832, that acids are capable of producing the 

 dehiscence of the pollen; but in the passage before us, he 

 compares the action of an acid, and of the stigma, for the 

 purpose of showing their difference, and tells us that the na- 

 tural tube grows at the expense of the fluidity of the stigma, 

 being obviously ignorant that this fluidity is acid, and capable 

 of acting as an acid on the pollen grains. If he was aware of 

 this, the onus lay on him to show, why the acid liquor on 

 the stigma should not act like acids elsewhere, but produce 

 a natural tube, instead of what he calls an artificial tube. It 

 may appear strange that he should be aware of the influence of 

 acids, and yet not examine the chemical reaction of the stig- 

 ma; but with this I have nothing to do; I knew the same 

 thing for six years, before the idea occurred to me, that it 



