Varietäten, Descendenz, Hybriden. 83 



Althaea rosea. History and morphology of double flowerdiscussed. 



Besides the sins^le and double ordinary Hollyhock, the newer 

 AUegheny Hollyhock [A. rosea var. fimbriatä) was used. The flowe- 

 ring raceme of this form is described as bearing Single flowers 

 above and double flowers below. The conclusions arrived at are 

 1. Singles breed true. 2. Highgrade doubles breed true. 3. F^ between 

 Singles and high grade doubles consists of low grade intermedia- 

 tes — the type occurring in the AUegheny Hollyhock. 4. These F^ 

 or AUegheny plants give high grade doubles, intermediates and 

 Singles probably in the ratio 1:2:1. The AUegheny Hollyhock is 

 thus evidently a heterozygote between double and Single as far as 

 this character is concerned. 



Carnation [Dianthus caryophylliis): the conclusions of the author 

 regarding this plant are 1. Doubleness is dominant. 2. All Singles 

 and certain {■:=. homozygous) doubles breed true. 3. Other (r= hetero- 

 zygous) doubles yield 3 d : 1 s. 4. The doubling is probably not a 

 simple process but one involving a number of associated changes 

 and therefore dependant on more then one set of allelomorphic 

 factors. The author doubts whether mere number of petals without 

 regard to consideration of either area or bulk can be safely used 

 as the sole criterion of comparison. 



Sweet William (Z). barbatus). The conclusions arrived at are: 

 1. Single form is usually hermaphrodite but certain individuals may 

 become female throughsuppression of the stamens. 2. Double flowered 

 individuals are mostly female through complete petalody of the 

 stamens. 3. When simple petalody of the stamens occurs, the double 

 usually Shows 15 „petals" in 3 alternating whorls. The number of 

 „petals" may be fewer owing to some normal stamens occurring or 

 more numerous owing to Splitting of the stamens. 4. All the doubles 

 investigated when fertilized with pollen from incompletely double 

 flowers yielded onl}'- double offspring. 5. Singles raised from com- 

 mercial seed supplied as double-producing seed invariably proved 

 to be heterozygous and yielded a mixed offspring in the ratio 

 3 s : t d. when selfed and 1 s : 1 d when fertilized with pollen from 

 incompletely double flowers. 6. The relation of Single to double is 

 evidently that of dominant to recessive, being thus the reverse of 

 that which obtains incarnation. W. Neilson Jones. 



Trow, A. H., On „Albinism" in Senecio vulgaris L. (Journ. of 

 Genetics. VI. p. 65—74. 1916.) 



A number of „white" seedlings occurred in the course of some 

 experiments which involved the crossing of species of Senecio. The 

 genetical behaviour of these „white" plants was peculiar in Ihat the 

 albinism proved to be a doubly recessive character, such as would 

 be represented genetically by aa bb. 



The nature of the phenomenon may be illustrated by the foUow- 

 ing results obtained in F2 as the result of crossing two of the white 

 segregates of 5. vulgaris, named provisionally by the author 5. 

 praecox and 5. lanuginosus, 



XTQ 91 \ Found greens: whites : : 688 : 39 

 ^^ I Calculated 15 : „ : : 682 : 45 \ 



• Seed 9 months old. 

 •fao qn \ Found greens: whites : : 537 : 28 i 

 ' Calculated „ : „ : : 530 : 35 f 

 W 13 greens : whites : : 142 : 1 Seed 21 months old. 



