466 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



in the daytime. This difference between the growth which takes place 

 during the day and the night cannot be attributed to the influence 

 of light and darkness respectively, as experiments showed very little 

 effect upon the growth when the roots were artificially darkened. 

 Most probably the higher transpiration during the day determines the 

 slower growth of the roots. No well-defined negative or positive 

 phototropism or geotropism is exhibited by these roots. — R. B. 



Cistus x Loreti (Bol. Mag. tab. 8490). — Garden origin. Family 

 Cistaceae. Cross between C. ladaniferus and C. monspe lien sis. Shrub, 

 4 feet high. Leaves 2J inches long. Inflorescence umbellate, 3-4 

 flowered. Petals 5, ij inch across, white, with yellow basal spot. . 



G. H. 



Citrus, A Knot of Citrus Trees caused by Sphaeropsis tume- 

 faciens. By Florence Hedges and L. S. Tenny (U.S.A. 

 Dep. Agr., Bur. PL Ind., Bull. 247). — Knots caused by the fungus 

 Sphaeropsis tumefaciens occur on orange, pomelo, lemon, tangerine, 

 and Citrus trifoliata. Affected branches are girdled by the tumours, 

 and the branch above the knot ultimately dies. Knots appear in 

 any season regardless of weather conditions, and trees of all ages are 

 attacked. 



There is no external evidence of the fungus, but microscopical 

 examination shows the presence of mycelium in all the different 

 tissues of the stem, producing black areas if present in abundance. 



The pycnidia, as they have been observed in the host, are sub- 

 globose, papillate, dark brown or black, ostiolate, closely crowded 

 together or solitary. They are at first covered by the epidermis but 

 finally break through the epidermis. The pycnospores are large 

 yellowish or colourless, and variable in size. Spermatia occur in the 

 pycnidia or in separate spermagonia, but their germination has never 

 been observed. The disease can spread from tree to tree, and the 

 author recommends the burning of all diseased tissue, and the careful 

 selection of sound trees for grafting purposes. — D. M. C. 



Citrus Fruits, Diseases of. By P. H. Rolfs, H. S. Fawcett, 



B. F. Floyds {U.S.A. Exp. Sin., Florida, Bull. 108; Nov. 1911).— 

 Various diseases of citrus fruits are described, also injuries due to 

 spraying and wrong treatment. 



Of the fungoid diseases two stem-end rots, Phomopsis sp. and 

 Diplndia natalensis (which cause great loss by dropping of the fruit), 

 the black rot inside the fruit at the stem end, and a third black rot 

 at the blossom end seem to be serious. 



During transit and in storage Penicillium italicum and Penicillium 

 digitatum, both wound parasites, are answerable for considerable 

 damage and loss. 



Methods of control are given when known. — D. M. C. 



