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JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



sport with horizontal leaves; hence he calls it " atavistic." In these 

 cases the horizontal position of the bough induces the leaves to become 

 horizontal too; but, as stated, only by twisting the petioles. In the 

 case of the common laurel, Prunus Laurocerasus, the horizontal boughs 

 have their leaves distichous while those on vertical shoots at the top of 

 a bush are pentasficlious , a much more important difference. 



Professor de Vries draws attention to the fact that many varieties, 

 and one may add species, are only found locally in very restricted areas 

 and adds: "In such cases transitional forms are always lacking, a 

 fact which proves pretty conclusively that such have not been produced 

 in the origination of the form." But they prove inductively that the 

 cause of their existence is the local conditions of their environment, 

 to w^hich they have responded. Such restriction of species is found, 

 e.g., among the 500 or more species of Erica at the Cape. One 

 I know of grows only on the rocks by a waterfall. It has lost the 

 typical needle-like leaf and has leaves of a short oval form. Instead of 

 being a xerophyte it has become more or less a hygrophyte. 



The young and older forms of foliage of Retinospora, the reversion 

 of spines to leaves in Berheris, &c., are referred to, on which Pro- 

 fessor de Vries observes: "These phenomena, however, fall mostly 

 within the sphere of systematic botany, and only concern the study 

 of variability in so far as they are dependent on external influences." 

 But this is the very matter the Professor should have especially studied, 

 as ecology lias proved how they are precisely the causes to be investi- 

 gated, for through the action of these, varieties and species of all sorts 

 arise. 



Here again the author misses the perception of the latter being the 

 universal cause of variation by response, or, to use Danvin's expressions, 

 the "direct action of changed conditons of life," which produces 

 " definite results," i.e., variations "without selection at all." 



The author gives an interesting section on striped flowers. Accord- 

 ing to Vilmorin they only occur on those species which have a white 

 variety, being naturally themselves whole coloured. Or, if a flower is 

 red and yellow, the uniform yellow may behave like w^hite in giving 

 rise to them. The first variety to arise is the w^hite or yellow. This is 

 constant from the first, according to the rule, as found also by Messrs. 

 Sutton — " Variations, not resulting from crossing, usually come true 

 from the first, as Primula sinensis " Coral-pink," sporting from " Crim- 

 son King." 



With regard to striping, Mr. Sutton tells me that he cannot explain 

 the cause, " though it sometimes results from crossing a dark with a 

 lighter variety ; and the remarkable feature is that the colour is not 

 necessarily weakened and generally diffused, but only restricted in 

 area." An example as the result of hybridization would seem to be 

 seen in Petunia violacea crossed by P. vijctagiiiiflora ; the deep violet 

 of the former is usually stiiped by broad bands of white from the 

 latter species. Professor de Vries' experience is that crossing has 

 only resulted in the production of self-coloured, and not variegated 



