NOTES AND ABSTRACTS, 
217 
normal conditions the physiological brakes are on at all times, more or less, for 
all animals and plants, and only when they are entirely or largely removed 
in particular areas, do we observe an unlimited cell proliferation resulting in the 
hasty and peculiar growths known as neoplasms, or cancers. The inhibition 
remover is one that acts locally % disturbing tissue equilibriums within limited areas. 
If the cause of cell proliferation in crown-gall is due to substances liberated 
in the cell by the parasite, they must be substances either identical with or at 
least not differing greatly in the physical or physiological action from those 
acting on the non-parasitized cell during normal growth and division. There is 
no evidence of chemical injury either in the tissues surrounding the crown-gall, 
or in the tumour cells themselves, since they grow and multiply with a rapidity 
resembling cells of normal young tissues. This removes from consideration 
actively (killing) poisonous substances. 
The questions to be answered are : 
1. What are the products of the bacterial metabolism of B. tumefaciensl 
2. Are any of these products capable of producing cell proliferation if injected 
into the growing plant ? 
We know that growth of B. tumefaciens in culture media of grape sugar and 
Witte's peptone causes formation of ammonia and alcohol and acetic acid, as 
well as carbon dioxide and primary and secondary amines. This production 
of acids and ammonia suggested to the author that tumours might be formed 
by the injection of such substances into growing plants. 
Experiments were therefore made by injecting into healthy Ricinus communis, 
and Nicotiana Tabacum and other species, various strengths of ammonia and 
ammonium salts ; and in many cases tumours were formed. Some striking 
micro-photographs of Ricinus stems with tumour are shown* 
The author concludes that these substances act osmotically rather than 
chemically in producing the tumours, and believes that as a result of the meta- 
bolism of an intracellular parasite or symbiont, together with the resultant 
counter -movements of water and food supply, such tumours are formed in 
crown-gall and presumptively also in animal neoplasms. 
A short list of literature is appended. — A. B. 
Crusoe's Island : Juan Fernandez. By J. Hutchinson (Gard. Chron. May 19- 
June 16, 191 7; with 9 figs,)- — An interesting account, chiefly historical. The 
botany is dealt within the last portion, commencing on p, 240, — E* A. B, 
Cucumber Disease caused by Ghoanephora Cucurbitarum. By F. A. Wolf 
(Jour.Agr. Res. viii. Feb. 1917, pp. 319-328 ; 3 plates). — The disease is commonly 
met with on cucumbers, where it causes a blight of the flowers and fruit rot. 
Infection appears to occur in the corolla and so passes into the ovary, being 
carried by various species of bees, beetles, and by wind. The fungus may also 
attack cotton, Althaea, and other Malvaceae. Sporangia, chlamydospores, and 
zygospores are produced, and may mature on cultures in 24 to 48 hours. Conidia 
are only known upon the affected parts of the diseased plants. — A. B. 
Cupressus glabra. By A. B. Jackson (Gard, Chron. March 3, 191 7, p, 95; 
with fig.). — The sixteenth of the critical notes on Conifers in this series, An 
American species related to C, arizonica, — E. A, B, 
Cypress and Juniper Trees of the Rocky Mountain Region. By George B, 
Sudworth (U.S. A . Dep. Agr., Bull. 207, July 17, 1915). — Describes the dis- 
tinguishing characters, distribution, and forest habits of all the known species 
of Cupressus and Juniperus growing within the Rocky Mountain region, 
([Arizona cypress grows in moist or rather dry, rocky, shaly, or gravelly soils 
on^mountain slopes, and in the bottoms and on the sides of canons, at elevations 
between 4,500 and 8,000 feet. It is especially fond of moist north-slope gulches 
and benches where the growth is more dense^than in drier situations, 
For the most part it forms pure or nearly pure stands, quite dense on the more 
favourable sites. The largest and best-formed trees occur on north slopes, in 
coves, and on benches in protected localities, where the soil is moist, deep, and 
more permeable, while short stunted trees are found in exposed places where 
the scanty soil is drier and less permeable. 
Smooth Cypress^ — The first reference to this new and handsome cypress was 
published in 1895, and was based on the discovery of a grove on Pine Creek at 
" Natural Bridge," Central Arizona, by Professor J, W, Tourney, who believed 
the tree to be a form of Arizona cypress. It was not distinguished from the latter 
tree, however, until February 1910, when it was named and described from a 
