SCIENTIFIC COMMITTEE. 
cxxxix 
caused by the fungus Rhytisma acerinum, in which the leaves were 
almost entirely covered by the black spots which the fungus produces. 
The fungus hibernates on the dead leaves on the ground, and pro- 
duces ascospores there which re-infect the tree in the succeeding year. 
Variegated Tropaeolums. — Col. H. E. Rawson, C.B., remarked that 
he found the plants of variegated T. tnajus which he showed at the last 
meeting liable to be attacked by black aphides, which congregated 
only on certain parts which were exposed to particular rays of light. 
Massonia jasminiflora. — Mr. Bowles exhibited a plant of this 
interesting species which had been figured in the Bot. Mag. t. 7465, 
and which grows on the veldt at the Cape, whence the bulb from which 
this plant was derived came. The white flowers, which rise but little 
above the deep green foliage, are very sweetly scented. It had 
flowered in a garden at Waltham Cross. 
Plantago lanceolata. — Mr. Bowles also showed a scape of Plantago 
lanceolata measuring over a yard in length, which Mr. P. D. Williams 
had found on a very cold, wet clay near Lanarth, usually regarded as 
an infertile spot. 
Colour Standards. — A letter from Mrs. D. F. Kerr, of Kelowna, 
B.C., aroused a discussion concerning existing colour standards and 
the criticisms to which they were open. It was thought, however, 
that the time was inopportune for attempting the necessary revision 
at present, desirable as the revision is. 
Gall on Rose. — Mr. Cocks, of Winnipeg, Canada, sent a gall from a 
Rose measuring about 3 inches in diameter, which Dr. Rendle took for 
further examination. 
Preservation of Green Colour in dried Leaves.' — Dr. A. B. Rendle, 
F.R.S., showed a series of Fern fronds, some of which had been dried 
and exposed to the light for three years, to illustrate the value of the 
copper acetate method of preserving the colour. He gave the follow- 
ing account of the method : — A stock solution is made by saturating 
commercial strong acetic acid with powdered copper acetate. For 
treatment, dilute the stock solution with water in the proportion of 
3 or 4 parts of water to one of stock solution. The solution is heated 
in a non-metallic vessel — a glass beaker being probably the most suit- 
able — to boiling-point ; the specimen is placed in the boiling solution, 
which is kept boiling, for a time varying from 1 minute to 40 minutes, 
according to the action of the copper salt upon the plant. If the 
action is proceeding satisfactorily, a period of 1 to 5 minutes should 
suffice ; the end of the operation is easily judged by the colour, or by 
treating two different specimens for different periods ; a specimen that 
by such comparison appears to require longer treatment can always be 
re-immersed to get the desired effect. Many plants, notably the leaves 
of evergreen shrubs, are more difficult and generally less satisfactory 
in the ultimate colour, probably owing to the presence of mucilaginous 
or decomposition products or tannins. These require long treatment, 
varying from twenty to forty minutes ; after the first immersion they 
turn yellowish, and then after action the yellow gradually gives place 
