128 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
I suppose few of us have ever asked why and how it comes about 
that a Rose is fragrant ; so let us for a moment turn, as Ruskin suggests, 
to consider the "invisible particles " which cause the scent of a Rose- 
leaf. Why does a Rose smell ? Whence is its scent ? Scientists 
tell us that it arises from an essential oil found in the papilliform 
epidermal cells on the upper surface of the petals, rarely in the cells 
on the under side. From an examination of the epidermis of the 
petals it was thought at one time that both sides were equally odori- 
ferous, but later investigations have shown that the volatile oil is 
secreted in and given off mainly from the tiny cells on the upper surface. 
It is also stated that the oil does not accumulate or take the form of 
drops, but is given off almost as soon as it is generated, and that the 
formation and dispersion by exhalation proceed almost simultaneously. 
Having realised that the cause of scent is an essential oil generated 
in the cells on the petals of a Rose we shall readily understand, what 
we know from observation to be a fact, that warmth is an important 
factor in fragrance. So also is a moist atmosphere. Not that tem- 
perature determines whether a Rose can be classed as scented or other- 
wise, but that it decides the rapidity with which the oil is generated 
and given off into the air. Hence on cool days scent is much less 
evident. These considerations probably explain what has been noticed, 
that Roses flowering under glass give off a greater amount of perfume 
than those cultivated in the open air — it is largely a question of 
warmth. Also the petals with the tiny cells are more perfect and 
undamaged by wind and weather. 
Something depends, too, on the age of the bloom : the petals of 
a Rose must be well developed before the highest degree of fragrance 
is attained. 
It is said that cut Roses placed in a vase diffuse their fragrance 
more powerfully than when growing on the plant, and there is no 
doubt that two or three fine specimens of ' Richmond ' or ' George 
Dickson ' will scent a room. So is the scent of Roses strongly diffused 
in the exhibition tent, where the conditions favour the rapid secretion 
and dispersal of the essential oil. In illustration of the capricious 
nature of perfume in Roses and the extraordinary complexity of its 
forms, I have seen it stated that in the whole list of Roses there are not 
two which develop precisely the same odour, but that in the same 
species and even on the same plant there are not found two flowers 
absolutely identical in scent, and even at different times of the day 
an individual flower will emit a different perfume. Probably this is 
rather a question of degree than of actual difference, and is related to 
temperature, the condition of the atmosphere, and the age of the 
flower. 
Warm climates are required for Roses cultivated commercially 
for the production of Otto of Roses, which is distilled from the petals. 
The industry is carried on in Persia, India, Turkey, extensively in 
Bulgaria, and in France. Since 1886 the finest Otto has been made 
near Leipzig in Germany by highly scientific methods, the Roses 
