646 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Mechanical Stimulus." Full descriptions of the various experiments made 

 and figures of the instruments used are given, but it is almost impossible 

 to give a short abstract of the paper. — G. S. S. 



Electricity, Trees felled by (Le Jard. December 20, 1903, p. 371). 



— Successful experiments have been made in felling trees by means of a 

 platinum wire raised by electricity to a white heat. This method takes 

 one-eighth of the time required to saw the tree down. — C. W. D. 



Entomology in New Jersey, Economic. By J. B. Smith (U.S.A. 

 St. Bd. Agric. New Jersey, Rep. 1902-3, pp. 101-8).— Mr. Smith 

 points out the need for constant attention to research work in economic 

 entomology. He reported on the partial success of the introduction of 

 the Chinese lady-bird (Chilocorus similis) into New Jersey for the sup- 

 pression of the San Jose scale. Mosquitos have been investigated 

 during the year, and it is stated that they hibernate in cellars. The 

 lime-sulphur-salt wash is recommended in preference to crude petroleum 

 as a remedy against scale. — F. J. C. 



Ericaceae, Dehiscence of Anthers and Development of Seeds 



in. By A. Artopoeus (Flora, vol. xcii., 1903, pp. 309-345 ; 84 cuts). — In 

 the Ericacece proper the role of dehiscence becomes specialised in the 

 epidermis, which has thus the character of a true exothecium, while the 

 endothecium progressively loses its function ; an intermediate state is that 

 of Erica and Rhododendron, where tissue resorption alone determines 

 dehiscence. Clethra remains in the primitive condition with a functional 

 endothecium, while Epacridacece and Pyrolacece (including Monotropa) 

 are at the other extreme. The nucellus produces a row of four mega- 

 sporocytes, of which the hindmost is functional as the embryo- sac ; the 

 rest of the nucellus is absorbed. Two multinuclear endosperm haustoria 

 are formed, one at either pole, and grow into the micropylar thickening of 

 the integument and the chalaza respectively ; traces of them may be 

 found in the ripe seed. Epacridacece reveal a similar pair of haustoria. 

 In the development of ovule to seed the Ericacece are true Sympetalce. 



M. H. 



Ethereal Oils and Allied Substances : their Action on Plants. 



By Arthur Heller (Flora, vol. xciii., 1904, pp. 1-31). — The author's con- 

 clusions are of especial interest from the frequent use of ethereal oils, 

 paraffin, and resin in insecticide spray ; and being the result of careful experi- 

 ment we reproduce them. The vapour of ethereal oils and volatile hydro- 

 carbons (such as paraffin) is very poisonous ; their action is less in the liquid 

 state and when dissolved in water. Plants which secrete oils are more 

 resistent to the action of their own oil. Ethereal oils can be taken up into 

 the living cell. Ethereal vapours pass most readily into the plant through 

 the ail spaces; the cuticle delays, but does not prevent, the entrance of 

 the oil. The vapours are first dissolved in the water of imbibition of the 

 cell-wall, and thence diffuse into its interior ; a dry membrane offers 

 less resistance than a saturated one. Oil-producing plants exhale less 

 oil when the conditions of life are unfavourable. Resins in solution are 

 not absorbed into the living cell; and paraffin is not taken up by the 

 living moss or fungus (Aspergillus Pcnicillium).—M. II. 



