180 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



the corolla has developed to some extent; and that sometimes it is 

 wanting when the corolla becomes like that of a snapdragon. More- 

 over, a complete peloric flower has five spurs, but three only are not 

 uncommon, showing that the " peloric energy " gradually affects the 

 rest of the petals. Professor de Vries appears to have observed these 

 facts. Since there are 130 species of Linaria, the " spur " must have 

 originated very early in the history of the genus, and the power to make 

 it has apparently become latent in every one. 



With regard to the variegation of leaves, after noticing that it may 

 be unilateral on a branch. Professor de Vries considers " the influence 

 of external conditions on the degree of variation. On this point the 

 literature is rich in contradictory information." As an example he 

 mentions the variegated horseradish, which in the shade is green but 

 in a cold frame or sunny situation is variegated. So if Fragaria indica 

 variegata "is to be nicely variegated it must be planted in good dry 

 soil, not too loamy or calcareous." 



" On variegated shrubs we often see that in the better-lighted parts 

 variegation is more intense and in the shaded ones less pronounced." 

 He mentions variegated comfrey and Samhucus nigra. He omits 

 the commonest of all, Aucuha japonica, the surface leaves of the bush 

 being always much more spotted with yellow than the deeper-seated 

 ones. 



This subject would seem to fall into line with Sorby's discovery 

 of an optimum of light desirable for every species; too much or 

 too little will reduce the power of making chlorophyll.'^ The 

 yellow colouring is therefore due to an excess of light ; just as it is in 

 early spring if the temperature be too low for vigorous growth of herbs. 

 In a section on external conditions and manuring he shows, with a 

 proliferous clover and silverweed with three or four petals instead of 

 five, that it is immaterial whether a monstrosity consists of more parts 

 or fewer; having once appeared, an increase of nourishment favours 

 the anomaly; thus the clover gave 6 per cent, in a sand bed and 12 per 

 cent, on the richer control. The Potentilla anserina gave 65 per cent, 

 on the well-manured and 49 per cent, on the unmanured. Similar 

 results occurred with Begonia Sedeni, &c. 



Lastly, hot and dry summers produced abundance of malformations 

 in 1866 and 1893 ; 1845 was a great year for peloric Calceolarias ; 

 1862 for central umbels in Auriculas. It has often been noticed how 

 a certain sport appears in many places in the same year. We may, 

 therefore, conclude that external conditions — though we may not be 

 able to trace the why and wherefore in every case — are the primary 

 cause of all kinds of teratological phenomena. And when once they 

 have appeared there follows an inherent tendency to repeat themselves 

 by heredity. 



There is, therefore, no necessity to assume any law of periodicity 



* " Comparative Vegetable Chromatology " [Proc. Royal Soc. vol. xxi., p. 442. 

 1873). 



