No. 603] 



BUD-VARIATION 



US 



most variations be produced in cell divisions previous to 

 the formation of the germ-cells? When recessive we 

 should not note them as bud-variations unless the plant 

 is heterozygous and the mutating cell gives rise to a 

 branch; when dominant we should only note them in the 

 latter eventuality. But if these mutating cells should 

 later give rise to germ-eells, the change would become 

 apparent in the progeny. 



We have still one other hypothetical case to consider. 

 It is said that some bud-variations are not transmitted 

 by seed. I have not been able to trace an authentic case, 

 but such is the general belief, fathered, I think, by Dar- 

 win. The usual citation is the nectarine, which sometimes 

 is said to give nectarines but at other times gives only 

 peaches. Whether trichome characters only behave thus 

 I do not know. But if that be true, we can understand 

 why if we refer to Winkler's work on the so-called graft- 

 hybrids. 



Winkler found that the most interesting of these pecul- 

 iar phenomena are caused by the tissue of one species 

 growing around the tissue of the other. He therefore 

 gave them the euphonious name of periclinal chimeras. 

 Cytological examination showed that the epidermal tis- 

 sues only are from one race, the remaining tissues being 

 from the other. It is really a s\Tnbiosis and not a union. 

 Now as the germ-cells are formed wholly from subepi- 

 dermal and never from epidermal tissues, the seeds of 

 these plants always produced seedlings like the type 

 forming the inner cell-layers. 



It seems probable that the production of the nectarine 

 may be analogous. If the change producing the nec- 

 tarine occurs after the epidermal tissue has been segre- 

 gated from other tissues, the cells which are ancestors 

 of the germ-cells should not be affected and the nectarine 

 s^eedlings would give peaches. If. on the other hand, the 

 '•1i:ni-T> producing the nectarine, lias (.(^ciirrod before any 

 <iu-]\ s('ore<ration, the progeny sexually produced should 

 m ])art l>e nectarines. 



