278 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY 



D. altaica differs by its erect growth ; white. 



D. arbuscula. There are two plants under this name, D. Laureola 

 and a garden form of D. cneorum. 



D. atropurpurea, Mezereum with purple-black leaves, a garden 

 form. 



D. Blagayana, an Austrian species, has attained large size at Edin- 

 burgh and Glasnevin. 



D. buxifolia, a miniature D. alpina. 



D. caucasica (D. salicifolia), distinguished from D. altaica by its 

 taller stature (4 to 5-feet plants have been known). 



D. Sophiae, between D. altaica and D. caucasica, leaves streaked 

 white and green, flowers; white scented. 



D. Gnidium, green flowers and ornamental foliage, grows in shade. 



D. hybrida (D. Dauphiniix D. Delphinii or D. indica), an Asiatic 

 shrub with glossy evergreen leaves and fragrant reddish- violet flowers. 



D. Laureola, and its var. Philippii of the Pyrenees, grow in shade, 

 green flowers and black berries. 



D. pontica, nearly related to the last. 



D. Mezereum is well known ; the D. odora of Japan and its var. 

 D. japonica are among the sweetest of the known flowers ; the first 

 has lilac, and japonica white flowers. 



D. oleoides (Greece), related to buxifolia. 



D. Pseudo-Mezereum, fragrant bright orange flowers. 



D. rupestris or petraea, flowers clear carmine, bushes dwarf and 

 close-growing. 



Propagation is by seeds, which take a year to germinate, by cuttings, 

 layers and grafting. 



They will all strike from cuitings. D. indica is the most difficult, 

 and may take two years to form roots. D. rupestris is the easiest. 



H. R. D. 



Dianthera americana, Black Knot Disease. By I. M. Lewis 

 (Mycologia, iv. pp. 66-71 ; March 1912 ; 4 plates). — Hypertrophied areas 

 occur on the internodes, and later the bark cracks and exposes the 

 causal fungus ; the surface becomes later distinctly roughened and 

 papillate, and the colour, at first grey, becomes jet black. The fungus 

 causing the disease is new, and is named Bagniesiela Diantherae. A 

 technical description is given. — F. J. C. 



Digitalis, Some Hybrids of. By W. N. Jones {Jour. Gen., 

 II., pp. 71-88; figs, and plates). — Reciprocal hybrids were obtained 

 between Digitalis purpurea and D. grandi flora (=Z). ambigua). They 

 are described and compared with the characters of the parents. It is 

 concluded that, in general, the expression of any character in these 

 hybrids is intermediate between its expression in the two parents, 

 the reciprocals differing from one another in that each shows a greater 

 resemblance to its seed parents, but in the case of some characters 

 there is complete dominance in the hybrids irrespective of whether 



