March 15, 1895.] 



SCIENCE. 



289 



similarities of these occasional leaves to 

 geologic types, but, so far as I recall, 

 they regard them as remnants or ves- 

 tiges of the ancient types rather than as 

 revei-sions to them. There is this impor- 

 tant diflference between a remnant and a re- 

 version. A remnant or rudiment is more 

 or less uniformly present under normal 

 conditions, and it should give evidence of 

 being slowly on the decline ; whilst a rever- 

 sion is a reappearance of wholly lost char- 

 acters under unusual or local conditions. 

 Now, mj^ chief reasons for considering these 

 sports to be reversions is the fact that thej' 

 occur upon the sterile and verdurous shoots, 

 the very shoots which are most likely to 

 vary and to revert because they receive the 

 greatest amount of food supply, as Darwin 

 has shown to be the case with independent 

 plants. And I am therefore able to make 

 still another analogy between phytons and 

 plants, and to illustrate again the essential 

 sameness of bud-variations and seed-varia- 

 tions. 



III. 



I now wish to recall j'our attention more 

 specifically to the subject of asexual varia- 

 tion. I have showai that no two branches 

 are alike any more than are any two plants. 

 I have also cited the frequent occurrence of 

 differences so marked that they are called 

 bud-varieties or sports. Carriere enumer- 

 ated over 150 of them of commercial im- 

 portance in France, and, as nearly as I can 

 estimate, there are no fewer than 200 named 

 horticultural varieties grown at the present 

 moment in this counti-y wliich had a like 

 origin. It is also kno«Ti that there are a 

 number of species in which seeds are prac- 

 tically unknown, and yet which run into 

 many varieties, as the pineapple, banana 

 and bread-fruit ; and note, if you will, the 

 great variations in weeping willows, a tree 

 which never fruits in this countiy. In our 

 gardens there are three or four varieties of 



the common seedless ' top ' onion, and I 

 have been able, by treatment, to vary the 

 root of the horse-radish, a plant which 

 rarely, if ever, produces viable seeds in this 

 climate ; and there are variable seedless 

 plants in our greenhouses. I might also 

 cite the fact that most fungi are sexless, so 

 far as we know, and yet they have varied 

 into innumerable sjiecies. You will be in- 

 terested in a concrete case of the apple. 

 The Newtown Pippin, which originated 

 upon Long Island, New York, has been 

 widely disseminated by graftage. In Vir- 

 ginia it has varied into a form known as 

 the Albemarle Pippin, and a New York 

 apple exporter tells me that it is a poorer 

 shipper than the Northern Newtown and is 

 not so long-keeping. In the extreme North- 

 western States the Ne\vtiOwn, while- it has 

 not been rechristened there, is markedly 

 unlike the Eastern fruit, being much longer 

 and bearing distinct ridges about the apex. 

 Finally, in New South Wales, the ridges are 

 more marked and other characters appear, 

 and the variety is there known as the Five- 

 crowned Pippin. This is not an isolated 

 case. Most Northeastern varieties of apples 

 tend to take on this elongated form in the 

 Pacific Northwest, to become lieavj- -grained 

 and coarse-striped in the Mississippi Valley 

 and tlie Plains, and to take other character- 

 istic forms in the higher lands of the South 

 Atlantic States. This asexual variation is 

 sometimes very rapid. An ilhistration came 

 directly under my own observation (and 

 upon wliich I have once rej)0rted) in the 

 case of the Chilian strawberry. Within 

 two years this plant, growing in my garden, 

 varied or departed from its wild type so 

 widely as to be indistinguishable from the 

 common garden strawberry, which has been 

 regarded by many botanists to be specifi- 

 cally distinct from the Chilian berry. This 

 remarkable departui'c, which has enabled 

 me, as I believe, to reconsti-uct the evolu- 

 tion of the garden strawben-y, was one in 



