NOTES AND ABSTRACTS. 



399 



2. External factors having important action on the resistance are as follows : 

 (a) wetting the leaves had a beneficial effect on the tomato ; [b) reduced tem- 

 perature and low light intensity during the day preceding fumigation increased 

 resistance. 



3. Injury closely paralleled the stomatal movement, increasing as the size 

 of stomatal aperture increased. 



4. A higher or lower water supply in the soil affected resistance, through 

 hastening or retarding the growth rate. Rapid-growing plants were susceptible 

 to injury, while slow-growing plants were more resistant. 



5. High-reducing sugar content seemed to be correlated with maximum 

 resistance. — R. J. L. 



Green Plant Bug, The Southern. By Thos. H. Jones (U.S.A. Dep. Agr., 

 Bur. Entom., Bull. 689, July 1918 ; 14 figs. ; 5 tables). — This pentatoid bug 

 (Negara viridula L.) causes severe injury to crops in the southern portion of the 

 Cotton Belt, attacking tomatos, potatos, beans, turnips, sweet potatos, mustard, 

 and a great variety of other plants. Injury is caused by the adults and nymphs 

 puncturing the plant tissue with their beaks and extracting the juices of young 

 growing shoots and developing fruits. 



Four natural enemies have been noted, the tachinid fly (Trichopoda pennipes 

 Fab.) apparently being the most important. 



Hand-picking and collecting eggs and nymphs is recommended, as sprays 

 are of very little use. — V. G. J. 



Greenhouses: Heating. By P. Rivoire (Rev. Hort. vol. xc. pp. 157-158). — 

 A mixture of coal-dust, slaked lime, and water, is made into a paste and cast 

 into briquettes in an iron mould. The slaked lime from 5 lb. of quick- 

 lime and two gallons of water are required for every 100 lb. of coal-dust. The 

 briquettes are dried in the shade for a week before use. — 5. E. W. 

 1 



Gunnera chilensis and manicata. By O. Stapf (Gard. Chron. Oct. 25, 1919 ; 

 p. 210, with fig.). — The best means for distinguishing these two species lies in 

 the inflorescences. The branches are slender, flexuous, up to 6 inches long in 

 G. manicata, but rigid, stout, and only 1-3 inches long in G. chilensis. The fruits 

 of the former do not assume the bright orange- red of the latter at Kew. — E. A. B. 



F. L. Ratgers (Gard. Chron. Nov. 8, 1919, p. 236) points out that G. manicata 

 ripens its fruits in Holland, and they are then of a dark orange colour. 



Also mature leaves of G. manicata are flatfish and unfolded, while those of G. 

 chilensis are more curled, crumpled, and smaller. — E. A. B. 



Hardening Process in Plants, and Developments from Frost Injury. By 



R. B. Harvey (Jour. Agr. Res. xv. pp. 83-112, Oct. 191 8 ; plates). — A study 

 of the effects of freezing on different plants and the resulting stimulation of 

 tissues, and in certain cases, death. The results of desiccation, plasmolysis, and 

 freezing are considered to be of a similar nature. — F. J. C. 



Heart Rot in Wood of the Western Hemlock (Tsuga heterophylla). By 

 Jas. R. Weir and E. E. Hubert (U.S.A. Dep. Agr., Bur. PL. Ind., Bull. 722, 

 Oct. 191 8, pp. 1-39 ; 13 figs.). — The fungus responsible for the decay of the 

 heart-wood of Tsuga heterophylla is Echinodontium tinctorium E. and E. (the 

 Indian paint fungus), and this enters the trees by wounds in the bark and dead 

 branches and soon extends to the heart- wood, which in time is entirely destroyed 

 by the disease. The extent of the decay increases with the age of the tree. Of 

 the total trees in Northern Idaho 97 per cent, were found to be attacked, and of 

 ten trees less than sixty years old, nine were infected. 



It is suggested that all infected trees should be destroyed by fire, as girdling 

 by the axe is not recommended. — A. B. 



Heat, Stem Lesions caused by excessive. By C. Hartley (Jour. Agr. Res. xiv. 

 PP- 595-604, Sept. 1918 ; figs.). — Death of seedlings of pines through damage 

 to the stem at soil level occurred in certain nurseries. The damage, which 

 had been called ' white spot,' was traced to excessive heat. — F. J. C. 



Heredity in Annual Beetroots and Carrots. By L. Daniel (Rev. Hort. 

 vol. xc. pp. 164-167 ; 5 figs.). — Biennial carrots come true from seed but annual 

 carrots show a great diversity of form, depending on the locality and the con- 

 ditions under which they are grown. Beetroots exhibit the same phenomena. 

 These results do not conform with Mendel's law. On no account should the 

 seed of the annual carrot be mixed with the biennial as it is worthless. — 5. E. W. 



