VARIATION 447 



The most difficult point to explain theoretically, is why bud- 

 variation is 7iot generally, but only occasionally, transmitted by 

 seeds. Even this may to a certain extent be accounted for by 

 the present theory. 



A bud is a growing point, enveloped by scales. It arises 

 from the apical cells, which produce the other cells of the shoot 

 by means of continual division, and these form the interfoliar 

 parts, leaves, and flower-stocks. In accordance with tlie 

 principle of the continuity of the germ-plasm, a part of the 

 * blastogenic ' germ-plasm of the apical cells must be transmitted 

 in an -unalterable' (' gebundenen ') condition to certain cells 

 of the shoot as accessory idioplasm (• Neben-Idioplasma") or 

 ' reserve ge?- //I -plasi/i.' From these cells it is passed on to the 

 sexual organs, where it is used for the formation of germ-cells. 

 This reserve germ-plasm remains undisintegrated, and is 

 perfectly distinct from, and independent of, the ' blastogenic ' 

 germ-plasm, which is gradually distributed during the ontogeny 

 of the shoot into groups of determinants. 



The fact that bud-variations are so rarely transmitted by 

 seeds seems to me to be owing to the cause just mentioned ; 

 for the majority of modified determinants required to make a 

 modification apparent may evidently be present in the ' blasto- 

 genic' germ-plasm, though absent in the reserve germ-plasm. 

 If we remember that these variations have been prepared long 

 beforehand in the germ-plasm, and that at first a few, and then 

 graduallv a larger number of determinants become modified in 

 a similar way, and that finally a fortuitous differential nuclear 

 division must, on our assumption, intervene before the ' blasto- 

 genic" germ-plasm of a certain apical cell can contain a majority 

 of modified determinants, it becomes comprehensible why the 

 reserve germ-plasm contained in this cell may behave differ- 

 ently, and contain only a few or none of the determinants 

 in question in a modified condition. We must not forget that 

 the influences which produce the variation are not those of the 

 nutrition of the bud in which the modification appears, but 

 those which affected the determinants during their long course 

 from the ancestral plant of a past generation to the bud in 

 which they now appear. 



This explanation seems to me to .sufficiently account for the 

 fact that the seeds which give rise to 'sports' indirectly, need 

 not necessarily transmit the modification. 



