18431862] POLLEN OF WHEAT 291 



said that he could not fix his mind on your book. He works Letter 618 

 himself beyond his mental or physical powers. 



And now, my dear Darwin, I may as well make a clean 

 breast of it, and tell you that I wrote the Nat. Hist. Review 

 notice too to me a very difficult task, and one I fancied I 

 failed in, comparatively. Of this you are no judge, and can 

 be none ; you told me to tell Oliver it pleased you, and so I 

 am content and happy. 



To W. E. Darwin. 1 Letter 619 



Down, 4th [about 1862-3?] 



I have been looking at the fertilisation of wheat, and I 

 think possibly you might find something curious. I observed 

 in almost every one of the pollen-grains, which had become 

 empty and adhered to (I suppose the viscid) branching hairs 

 of the stigma, that the pollen-tube was always (?) emitted on 

 opposite side of grain to that in contact with the branch of 

 the stigma. This seems very odd. The branches of the 

 stigma are very thin, formed apparently of three rows of cells 

 of hardly greater diameter than pollen-tube. I am astonished 

 that the tubes should be able to penetrate the walls. The 

 specimens examined (not carefully by me) had pollen only 

 during few hours on stigma ; and the mere suspicion has 

 crossed me that the pollen-tubes crawl down these branches 

 to the base and then penetrate the stigmatic tissue. 2 The 

 paleae open for a short period for stigma to be dusted, and then 

 close again, and such travelling down would take place under 

 protection. High powers and good adjustment are necessary. 

 Ears expel anthers when kept in water in room ; but the 

 paleae apparently do not open and expose stigma ; but the 

 stigma could easily be artificially impregnated. 



If I were you I would keep memoranda of points worth 

 attending to. 



1 Mr. Darwin's eldest son. 



2 See Strasburger's Neue Untersuchungen iiber den Befruchtungsvor- 

 gang bei den Phanerogamen, 1884. In Alopeciints pratensis he describes 

 the pollen as adhering to the end of a projection from the stigma where 

 it germinates ; the tube crawls along or spirally round this projection 

 until it reaches the angle where the stigmatic branch is given off; here it 

 makes an entrance and travels in the middle lamella between two cells. 



