4l6 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Hamamelis vernalis. By L. Chenault {Rev. Hort. vol, xcii. p. 47 ; 2 figs.)— 
This Hamamelis is widely distributed in the States of Missouri, Arkansas, and 
Louisiana. It is about 6 feet high. The leaves are bluish green on the upper 
surface and pale green underneath. In January it is covered with axillary 
groups of sweet-scented, reddish brown flowers. — S. E. W. 
Hardiness. By C. B. Waldron [Iowa State Hort. Soc. Rep., 1918, pp. 115- 
119). — Selection does not appreciably affect the hardiness of plants. Early 
maturity is an important factor in adapting plants to a cold climate. Exposure 
to frost removes moisture from plant cells and deposits it in the form of ice in 
the intercellular spaces. In order that a plant may survive the winter, it must 
retain sufficient moisture to enable it to resume activity in spring, ^^rotection 
is afforded by wind screens and by mulching, which delays freezing about the 
roots. Hardy hybrids can only be produced when at least one of the parents 
is hardy.— S. E. W. 
Haworthia Chalwini Matloth et Berger. By C. H. Wright {Bot. Mag. t. 8828 ; 
Dec. 1919). — A curious columnar plant with fleshy purplish -brown white-warted 
imbricate leaves. Suitable for cultivation in the succulent house and native of 
S. Africa.— F. /. C. 
Hawthorns as Hosts of Apple, Pear, and Quince Pests, Wild. By W. H. 
Wellhouse {Jour. Econ. Eniom. 13, Oct. 1920, pp. 388-391). — The author states 
that 374 species of insects are known to feed on Hawthorns, of which 210 species 
are found in the United States. Six species of serious pests of Hawthorn 
in the States may at any time be expected to become pests of cultivated fruits. 
Over one hundred species feed on both Apple and Hawthorn, of which a 
list of over twenty-five is given in the text. 
Not only do Hawthorns act as native hosts for insects, but also for cankers, 
blights, and rusts. It is suggested that either these plants be abolished as hedge 
plants, or that they be sprayed together with the orchards. — G. F. W. 
Heracleum persieum giganteum. By A. Van den Heede {Le Jard. vol. 
xxxiv. p. 133 ; I fig.). — The largest and most ornamental of the Umbelliferae 
is Heracleum persieum giganteum. Its large digitate leaves exceed a yard in 
length and half a yard in width. In spring the rate of growth is amazing ; 
it attains a height of 10 feet and is surrounded by an umbel of snow-white 
flowers, 3 feet wide. The plant thrives in deep rich soil and is easily raised 
from seed. — 5. E. W. 
Hoheria populnea var. laneeolata Hooker. By W. J. Bean {Bot. Mag. t. 
8843; June 1920). — Hardy in the south of England, where it forms a graceful 
and attractive late-flowering tree, but needing a greenhouse near London. 
The foliage is narrower than in the type and the white flowers rather smaller. 
F. J. C. 
Hop, Forms of, Resistant to Mildew. By E. S. Salmon {Ann. Appl. Biol. 
vol. V. IsTos. 3 and 4, April 1919, pp. 252-260). — -Certain seedlings of the wild hop 
are persistently immune to the attacks of mildew when grown in the greenhouse. 
Other seedlings under the same conditions and of the same parentage are very 
susceptible. Certain of the immune seedlings are also resistant in the open air 
under normal cultural conditions, while others are susceptible in the hop garden. 
The change in immunity is apparently associated with the changes in temperature, 
R. C. S. R. 
Hydrocyanic Acid, Fumigation with Liquid. By H. J. Quayle {U.S.A. 
Exp. Stn. California, Bull. No. 308, June 1919, pp. 393-407; 4 figs.). — This 
highly poisonous chemical was first used experimentally in 191 6, and on a 
commercial scale in 191 7 for fumigating Citrus trees in California. 
It is a colourless liquid, less than three-fourths the weight of water (Sp. G. 
0 6969 at 18° C), boiling at 26 5° C, highly volatile, the gas being quickly 
given off from the surface of the liquid, and its use is therefore attended with 
very great danger to the operator. Pot generators kill best at the bottom of 
the tree, but the liquid at the top ; 20 c.c. of liquid HCN (96-98 per cent.) 
equal i ounce of sodium cyanide as it is generally used. — G. F. W. 
Ilex verticillata A. Gray. By W. J. Bean {Bot. Mag. t. 8832 ; March 
1920). — This American deciduous holly is well known in English gardens. It 
is particularly valuable when it bears its bright scarlet berries (to induce the 
production of which it requires full exposure to the south). There is a variety 
with yellow fruit called chrysocarpa. — F. J. C. 
