358 JOUENAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The author describes and figures the staminate and ovuhite cones. 

 Ihe seeds germinate as soon as they are ripe and may have no resting 

 period; but seeds of Dioon, nearly three years old, germinated. The 

 leaflets of the seedling are markedly different from those of the adult. 



C. mexicana grows best in well-shaded, neither very dry nor very 

 wet, conditions. The development of pollen and the processes of 

 fertilization are fully described. The sperms are 220 /n in diameter 

 and 185 /u in length (in Zamia 306 and 332 /i). They swim rapidly, 

 bumping against each other and against the sides of the tube. 

 Individuals have been observed in movement for six hours. 



The embryo is also fully described. — -G. F. S. E. 



Cereus Silvestrii {Bot. Mag. t. 8426). — Argentine Eepublic. 

 Family Cactaceae; tribe Echinocacteae. Herb; prostrate, succulent. 

 Stem inches long; flowers showy, 1| inch across, brilliant orange- 

 scarlet. — G. H. 



ChapaPPal. By Fred G. Plummer {U.S.A. Dep. Agr., Forest 

 Service, Bull. 85; July 17, 1911). — The name Chaparral is not very 

 familiar, and may best be described as a mixed forest of stunted trees, 

 and is the result of peculiar climatic conditions. The trees are small, 

 with gnarled trunks and boughs, principally evergreen, and consist 

 mainly of four species of oak, the Californian laurel, and Castanopsis 

 chrysophylla, and many other shrubs and low-growing trees. In addi- 

 tion to conserving the water-supply the Chaparral 's chief utility lies in 

 its value as fuel and for fencing and forage. — A. D. W. 



Citrus, Scaly Bark or Nail-Head Rust. By H. S. Fawcetfc 

 (U.S.A. Exp. Stn., Florida, Bull. 106, June 1911).— This disease is 

 due to a variety of Cladosporium herharum, named by the author C. 

 herharum var. citricolum. It attacks fruit and bark, and appears 

 mainly on sweet orange trees. 



The remedies recommended are : — ■ 



(i) Top working — i.e. grafting grape fruit, mandarins and 



tangerines instead of other sweet oranges. 



(ii) Heading back and treatment with Bordeaux mixture. 



(iii) Spraying to prevent the fruit spotting. 



(iv) Pruning out of dead wood and badly diseased limbs. 



Good figures are given illustrating the life history of the fungus and 

 the effects of the disease and the preventive treatments on ,the host 

 trees.— I). M. C. 



Citrus Tree Scale. By 0. Brooks {Agr. Gaz. N.S.W. vol. xxii., 

 pt. xii., p. 1072).— A mixture of 1 gallon of red oil, 2 lb. of soft 

 soap in 35 gallons of water, is effective in killing scale on Citrus trees. 

 It should not be used after soda wash. — ^S'. E. W . 



Club-root, The Comparative Susceptibility of Cruciferous 

 Plants to Plasmodiophora brassicae. By G. C. Cunningham 

 {PhytopatJwlogy, ii. pp. 138-142; Aug. 1912). — The author concludes 



