220 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
Underneath the whole insect is rich orange-red. Aberrations in colour are not 
frequent but exist, as the rearing of a wholly black female would indicate. The 
fore wings are transparent, opalescent, with black borders and prominent discal 
mark ; the hind wings transparent, with slight discal mark and narrow black 
margin. Destruction of the larva is the only remedy that can be used to reduce 
an infestation. That the financial loss caused by Sesia novaroenis in Douglas fir 
product is great, and represents a greater leak in profits to manufacturers 
than any other avoidable item, is evident, — A* D, W t 
Dusting and Spraying of Stock Nursery. By V. B. Stewart {U,S.A. Exp. 
Stn. } Cornell, Bull. 385, Jan. 1917, pp. 338-361 ; 9 figs.) — The results of ex- 
periments during 191 5 and 191 6 indicate that the application of suitable powdered 
materials, with air as a carrier, will control certain leaf diseases of nursery stock 
as well as the commonly employed fungicide applied as a spray with water as a 
carrier. 
The dust mixture of 90 parts of finely divided sulphur (200 meshes to 1 inch) 
and 10 parts of equally finely powdered arsenate of lead controlled the leaf 
diseases of horse-chestnut, currant, plum, cherry, quince, and rose in the nursery, 
and it is reasonable to suppose that similar results might be obtained for such 
diseases on mature trees in orchards. 
The dusting method is more expensive, but the applications can be made 
in a much shorter time and more thoroughly than by spraying. Great care 
should be taken that only extremely finely ground materials are used in dusting 
mixture, as only such material will adhere to the foliage. 
Experimental work is suggested to determine the value of this process in the 
control of other diseases and to lessen the cost as far as possible, — A. B s 
Elsholtzia Stauntoni. {Le J ard. vol. xxxi. p. 825 ■ 1 Q.g.)—Elsholtzia Staun- 
toni is a hardy shrub from Mongolia ; it is about three feet high, and bears clusters 
of dark pink flowers in September and October, The leaves are aromatic. 
5, E % W» 
Endemism and the Mutation Theory, On. By k. N, Ridley [Ann. Bot. 
vol. xxx. no. cxx: Oct. 1916). — This paper controverts the opinions of Dr. J. C. 
Willis, published in " Ann. Roy. Bot. Gard. Perad." vol. iv. p. 2, and in " Ann, 
Bot." vol. xxx. 1916, p. 1, which deals with the rise and fall of species in Ceylon. 
Dr. Willis's views are, briefly, that it will need a geological submergence or 
some such accident to kill out a very common species ; that endemic species 
are the youngest, and of these the very rare the most recent ; that all mutations 
are at once fixed, and the new form will not revert to the old one ; that the 
theory of Natural Selection does not hold good. 
The author quotes much evidence of a contradictory nature to the above. 
He cites the case of Hedychium coronarium L. and H. flavescens, both con- 
spicuously abundant round Peradeniya and Kandy in 1888, which had entirely 
disappeared in 191 3 without any apparent reason. He mentions, as examples 
of the destruction of species by enemies such as insects, fungi, and bacteria, 
the shrub Lantana mixta, at one time very common all over the waste ground 
in Singapore, which became comparatively scarce owing to the ravages of a 
small green bug that attacked the young fruits and thus prevented seed pro- 
pagation ; and the white-tailed rat of Christmas Island, counted in millions in 
1886, but exterminated by 1904, supposedly by the brown rat introducing some 
bacterium (possibly the plague). The destruction of plants by man may be 
effected by plantations on a large scale and by destroying forests, and it may be 
brought about by climatic changes, e.g. the disappearance of the epiphytic fern 
Poly podium sinuosum from gardens of Singapore in 1905, after an extraordinary 
dry and hot spell lasting for a month or two, and the palaeobotanic records reveal 
innumerable instances of the extinction of species without any evidence of 
geological cataclysms in all such cases. 
Endemics are the relics of an old flora rapidly disappearing. Natural Selection 
is the only theory at present which accounts for the adaptation of plants to their 
surroundings, and in this Dr. Willis's mutation theory entirely fails, for it cannot 
explain, for instance, why Calophyllum inophyllum, whose fruits are adapted 
for sea dispersal, occurs only on the sea shore, or why Crinum asiaticum, with 
flowers only fertilizable by a crepuscular sphingid, only opens its flowers exactly 
at the time of the appearance of the moth. With regard to mutations, every 
botanist knows that variations occur in plants which do not appear again in 
their offspring. The Lalang Grass of Malay is referred to as showing how a 
plant may adapt itself to nearly any conditions. It possesses an underground 
rhizome which can flourish at a depth of sixteen inches, and, if dug up, any 
