January, 1912.] 



47 



Scientific Agriculture. 



waste plants can only be attained by 

 great labour extended over a va9t period 

 of time. Conceivably that view i9 

 correct, but no one acquainted with 

 modern genetic science can believe it 

 without most cogent proof. Far more 

 probably we should regard these rogues 

 either as the product of a few definite 

 individuals in the crop, or even as chance 

 impurities brought in by accidental 

 mixture. In either case they can pre- 

 sumably be got rid of. I may even go 

 further and express a doubt whether 

 that degeneration which is vaguely sup- 

 posed to be attendant on all seed crops is 

 a physiological reality. Degeneration 

 may perhaps effect plants like the potato 

 which are continually multiplied asexu- 

 ally, though the fact has never been 

 proved satisfactorily. Moreover.it is not 

 in question that races of plants taken 

 into unsuitable climates do degenerate 

 rapidly from uncertain causes, but that 

 is quite another matter. 



The first question is to determine 

 whether a given rogue has in it any 

 factor which is dominant to the corre- 

 sponding character in the typical plants 

 of the crop. If it has, then we may feel 

 considerable confidence that these rogues 

 have been introduced by accidental 

 mixture. The only alternative, indeed, 

 is cross-fertilisation with some distinct 

 variety possessing the dominant, or 

 crossing within the limits of the typical 

 plants themselves occurring in such a 

 way that complimentary factors have 

 been brought together. This last is a 

 comparatively infrequent phenomenon, 

 and need not be considered till more 

 probable hypotheses have been disposed 

 of. If the rogues are first crossed the 

 fact can be immediately proved by 

 sowing their seeds, tor segregation will 

 then be evident. For example, a truly 

 round seed is occasionally though very 

 rarely found on varieties of pea which 

 have wrinkled seeds. I have three times 

 seen such seeds on my own plants. A 

 few more were kindly given me by Mr. 

 Arthur Sutton, and 1 have also received 

 a few from M. Philippe de Vilmorin— to 

 both of whom I am indebted for most 

 helpful assistance and advice. Of these 

 abnormal or unexpected seeds some died 

 without germinating, but all which did 

 germinate in due course produced the 

 normal mixture of round and wrinkled, 

 proving that a cross had occurred. 

 Cross-fertilisation in culinary peas is 

 excessively rare, but it is certainly some- 

 times effected, doubtless by the leaf- 

 cutter bee (Megachile) or a humble-bee 

 visiting flowers in which for some reason 

 the pollen has been inoperative. But in 

 peas crossing is assuredly not the source 



of the ordinary rogues. These plants 

 have a very peculiar conformation, 

 being tall and straggling, with long 

 internodes, small leaves, and small 

 flowers, which together give them a 

 curious wild look. When one compares 

 them with the typical cultivated plants 

 which have a more luxuriant habit, it 

 seems difficult to suppose that the rogue 

 can really be recessive to such a type. 

 True, we cannot say definitely a priori 

 that any one character is dominant to 

 another, but old preconceptions are so 

 strong that without actual evidence 

 we always incline to think of the wilder 

 and more primitive characteristics as 

 dominants. Nevertheless, from such 

 observations as I have been able to 

 make, I cannot find any valid reason 

 for doubting that the rogues are really 

 recessives to the type. One feature in 

 particular is quite inconsistent with the 

 belief that these rogues are in any 

 proper sense degenerative returns to a 

 wild type, tor in several examples the 

 rogues have pointed pods like the 

 cultivated sorts from which they have 

 presumably been driven. All the more 

 primitive kinds have the dominant 

 stump-ended pod. If the rogues had the 

 stump pods they would fall into the 

 class ot dominants, but they have no 

 single quality which can be declared to 

 be certainly dominant to the type, and I 

 see no reason why they may not be 

 actually recessives to it after all. 

 Whether this is the true account or not 

 we shall know for certain next year. 

 Mr. Sutton has given me a quantity of 

 material which we are now investigat- 

 ing at the John Innes Horticultural 

 Institution, and by sowing the seed of a 

 great number of individual plants 

 separately I anticipate that we shall 

 prove the rogue-throwers to be a class 

 apart. The pure types then separately 

 saved should, according to expectation, 

 remain rogue-free, unless further sport- 

 ing or fresh contamination occurs. If it 

 prove that the long and attenuated 

 rogues are really recessive to the shorter 

 and more robust type, the case will be 

 one of much physiological significance, 

 but I believe a parallel already exists 

 in the case of wheats, for among 

 certain crosses bred by Prof. Biff en, 

 some curious spelt-like plants occurred 

 among the dervatives from such 

 robust wheats as Rivet and Red Fife. 



There is another large and important 

 class of cases to which similar consider- 

 ations apply. I refer to the bolting or 

 running to seed of crops grown as bien- 

 nials, especially root crops. It has 

 hitherto been universally supposed that 

 the loss due to this cause, amounting in 



