l8 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
In each case the organism was isolated in pure culture and the disease 
was subsequently reproduced artificially upon inoculation. To what 
extent is spotting in British collections due to bacteria ? In one 
particular spot of Odontoglossum first but incompletely described 
in the Gardeners' Chronicle * — a pellucid spot with a dark centre — 
the agency of bacteria is already suspected. First recorded only on 
Odontoglossum Uro-Skinneri, it is now found on several Odonto- 
glossum species and hybrids, including Odontoglossum crispum, 
0. X Loochristiense , 0. X Thwaitesii, 0. eximium, and in the hybrid 
genus Odontioda, for example Odontioda X "Euterpe" (= Odonto- 
glossum Uro-Skinneri X Cochlioda Noezliana), also in species of 
Oncidium, the hybrid genus Oncidioda, and in Cattleyas. It is surely 
important for Orchidists to know definitely whether this spotting is 
of bacterial origin or not ; if the latter, attention to cultural conditions 
alone will eliminate the trouble, and there would be no need for anti- 
septic treatment ; if the former, precautions should be taken to 
prevent the spread of the spot from one plant to another and from 
one collection to another. 
Amongst the diseases which have remained practically unstudied 
is a wilt of Clematis ; the leaves first droop and wither and then the 
stem dies ; the roots are frequently affected with a black rot, apparently 
of a bacterial nature. Here it is important to know whether the 
wilt and root-rot are due to the same cause, and upon this, I am told, 
depends the issue as to whether the use of a favourite Clematis stock 
shall or shall not be discontinued. 
In attempting to avert or mitigate maladies of plants, one must, 
as in human diseases, direct special attention to the needs of the 
body and the conditions under which health is best maintained ; in 
plants, unsuitable climate, inclement weather, insanitary surroundings, 
undue competition with surrounding plants, improper, injudicious, 
or unsuitable grafting or budding, planting, tending or feeding render 
the organism more or less susceptible to ailments, trivial or serious. 
Perhaps one could check many diseases if it were only known exactly 
what factor is wrong and if one possessed the means to set it right ; 
but there are certainly many that cultural skill alone cannot subdue. 
The horticulturist may be to a certain extent the victim of his 
environment, which perhaps favours outbreaks of disease. His soil 
perchance shelters the potato tumour (Chrysophlyctis endobiotica) or 
canker (Spongospora Solani) or finger-3ind-toe(Plasmodiophora Brassicae) 
organisms ; or he may be the victim of his own habits or design ; 
he may, by cutting back hard when removing rose blooms, and 
incidentally foliage, weaken the plant and render it more susceptible 
to mildew, or by excessive removal of Chrysanthemum foliage pre- 
dispose the plant to rust, or by disbudding Peaches leave wounds open 
to the ingress of a parasite, or by removing immature figs f provide 
* " Leaf-spot of Odontoglossum Uro-Skinneri," Gard. Chron. March 6, 1909, 
P- 145- 
f Several instances of canker at Wisley could be traced to the scars left 
on the branches by the removal of figs. 
