840 LAWS OF VARIATION. Chap. XXVI 



broader pods than its parent. Now Mr. Masters, of Canterbury, a 

 careful observer and a raiser of new varieties of the pea, states '^^ 

 that the Blue Imperial always has a strong tendency to revert to 

 its parent-stock, and the reversion "occurs in this manner: the 

 *' last (or uppermost) pea in the pod is frequently much smaller 

 " than the rest ; and if these small peas are carefully collected and 

 ** sown separately, very many more, in proportion, will revert to 

 *' their origin, than those taken from the other parts of the pod." 

 Again, M. Chate ^^ says that in raising seedling stocks he succeeds 

 in getting eighty per cent, to bear double flowers, by leaving only 

 a few of the secondary branches to seed; but in addition to this, 

 " at the time of extracting the seeds, the upper portion of the pod 

 " is separated and placed aside, because it has been ascertained 

 " that the plants coming from the seeds situated in this portion of 

 " the pod, give eighty per cent, of single flowers." Now the pro- 

 duction of single-flowering plants from the seed of double-flowering 

 plants is clearly a case of reversion. These latter facts, as well as 

 the connection between a central position and pelorism and pro- 

 lification, show in an interesting mauner how small a difference — 

 namely, a little greater or less freedom in the flow of sap towards 

 one part of the plant — determines important changes of structure. 



Analogous or Parallel Variation. — By this term I mean 

 tliat similar characters occasionall}'' make their appearance 

 in the several varieties or races descended from the same 

 species, and more rarely in the offspring of widely distinct 

 species. We are here concerned, not as hitherto with the 

 causes of variation, but with the results ; but this discussion 

 could not have been more conveniently introduced elsewhere. 

 The cases of analogous variation, as far as their origin is 

 concerned, may be grouped, disregarding minor subdivisions, 

 under two main heads ; firstl}'-, those due to unknown causes 

 acting on similarly constituted organisms, and which con- 

 sequently have varied in a similar manner ; and secondly, 

 those due to the reaj)pearance of characters which were 

 possessed by a more or less remote progenitor. But these 

 two main divisions can often be separated only conjec- 

 turally, and graduate, as we shall presently see, into each 

 other. 



Under the first head of analogous variations, not due to reversion, 

 we have the many cases of trees belonging to quite different orders 

 which have produced pendulous and fastigate varieties. The beech, 



2^ ' Gardener's Chronicle,' 1850, p. ^^ Quoted in ' Gardener's Chron.,* 



198. 1866, T,. 74. 



