BOTANY 213 



author in this paper suggests might be based on the parallehsm 

 in variation to which Eimer and others have previously directed 

 attention. 



The strikingly parallel series of varieties in the different 

 species of Wheat ; in Hordeuni vitlgare and H. distichum ; in 

 Agropymm repcns and A. cristatwn, of which fourteen out of 

 fifteen known variants are found in both species ; Cucurbita 

 pepo and C. maxima ; are all instanced as cases where related 

 species have been shown to produce exactly parallel series of 

 variants. 



Similarly in distinct genera, Secale and Triticitm exhibit 

 no less than thirty-four varietal types of a parallel character. 

 Indeed, the discovery of eligulate types of Wheat actually led to 

 their being sought and found in the Rye. Very striking illustra- 

 tions are afforded by Ervum. lens, Vicia saliva, Pisuni salivum, 

 and Lalhyrus salivus. All these exhibit parallel variations with 

 respect to colour of flowers, shape and colour of seeds, height, 

 period of development, etc. 



Parallelism in distinct famihes is illustrated by the wide- 

 spread occurrence of albinism, gigantism, nanism, fasciation ; 

 root types in Chenopodiacese (Beta), Cruciferae (Brassica), and 

 Umbelliferae (Daucus) ; peloria in zygomorphic flowers, etc. 



Mimicry is held to be a result of selection of these parallel 

 variations, of which a striking case is afforded by Ervum lens 

 and Vicia saliva. Here the methods of cleaning by screening 

 and hand picking have resulted in the selection of seed types 

 of the latter which are indistinguishable — alike in form, size, 

 and colour — from those of the former. 



Thus the variations of species and genera are held to be 

 members of a definite series comparable to those of the chemist : 

 " Knowing a succession of varieties in one genus or Linneon, 

 one can forecast the existence of similar forms and even similar 

 genotypical differences in other genera and Linneons." Once 

 this fundamental principle is estabhshed, then the simplification 

 of nomenclature on this basis need be merely a matter of time. 



A genetical study of variegated plants of Chlorophylum 

 has been carried out by Collins {Journal of Genetics, vol. xii, 

 pp. 1-17) working with the wholly green C. elatum and its two 

 variegated forms with a white margin and white middle to the 

 leaves respectively. The seedhngs produced by selfing the 

 variety with a white margin are wholly green, as also are those 

 of the type form. Selfing the variety with a white middle 

 region resulted in the production of seedlings all of which were 

 albino. The corresponding form of C. comosum selfed gave 

 sixty-six albinos, two variegated and one green. 



Various crosses yielded a small proportion of variegated 

 seedlings, but these^ all showed variegations of an irregular 



