W. Batkhon and Ida Sutton 201 



doubles gives scarcely anything but extreuu* doublcB. Slightly ]>c*tal(xlic 

 plants came also oocanionally, among largt> nunilM^ni of HJnglcH, in fauiili<« 

 raised from DavUii female fcTtilimnl with |>ollc'n of heterozygouH plantn 

 {Ft from double x ningle (f). Whon thi» jMillon of Daviini in uwhI on 

 such Fi plants the proportion' of recesMive, doublf-bi'uring, ova, of coiirmj 

 appears ; and since })erfectly reliable {wllen of doubles is ditticult to 

 obtain, the {)ollen of Davisii may be substituti'd for it. 



AIUt discovering the |x»culiar genetic constitution of l)av\mi we 

 naturally expt»cted that the results of reciprocal crosses mjule between 

 doubles and F, plants (from double x single) would at least 8*>metimes 

 show linkage of doubleness with either the male or the female side. 

 For this investigation a considemble amount of material is now available 

 and we are satisfied that in general heterozygotes do not show any 

 regular phenomenon of this kind. In contrast however to the usual 

 absence* of consistent sex-linkage, one plant raised from the female side 

 of Davisii fertilised by Lloydii was provcKl U) possess such sex -linkage, 

 though less complete than that of Davisii itself. The plant, self- ferti- 

 lised, set badly and only 2 plants (singles) were thus raised. As regards 

 its female side we have the evidence that with Davisii jwUen it gave 

 11 singles, and with Lloydii pollen 5 singles and 1 slightly petahxiic, 

 from which it may be inferred that the ovules were at all events 

 predominantly single-bearing. The male side tested on Lloydii gave 

 27 doubles, 14 half doubles and 5 slightly petalodic (see Nos. 23 — 26 in 

 Table on p. 20(5). 



As to the presence of sex-linkage in other heterozygous individuals 

 the evidence is as yet conflicting. Some plants show it, whereas others 

 do not, and we cannot as yet perceive any circumstance either in the 

 way in which the plants were made up or in any other resjiect which 

 accounts for these differences. We give in the Table (Nos. 31 to 45 

 on p. 207) specimens of these various behaviours. 



The case naturally recalls other examples in which sex-linkage has 

 been observed in plants. In three of these the male side has been 

 specially distinguished as being associated with the recessives, though 

 whether this is an accidental circumstance due to the way in which the 

 plants were originally bred cannot yet be declared, but in Petunia, as 

 shown by Miss Saunders singleness, the dominant, was carried by all the 

 poll en -grains, and by some only of the ovules of the single-tlowered plants. 

 In Matthiola the pollen was all double and for the most jxirt wirrying 

 cream plastid-cr>lour (Saunders); and in a plant of Campanida carpatica 

 ' This pro|>ortion, as Table II exemplifies, is appan'Utlv quite irregular. 



