Ernest Warren 
309 
2. The Presence of Brown Spots. 
Among the various families there occurred plants with white corolla which 
possessed brown or greenish spots in place of the usual dark-purple spots. Such 
brown-spotted flowers only occurred when the corolla was white. If there was 
the faintest trace of purple on any part of the general surface of the corolla the 
spots were almost invariably purple. On the other hand the intensity of the 
colouration of the spots appeared to be in no way related to the intensity of the 
general colouration of the corolla, since some of the darkest coloured spots were 
found in flowers with an otherwise white corolla. In the terminology of the 
Mendelians it may be said that distinct factors control the general colouration of 
the corolla and the colour of the spots. 
In this connection it is interesting to remember that the general colouration 
of the corolla is due to coloured sap in the cells of both the outer and inner epidermis 
of the flower, while the colouration of the spots arises through the colour in the inner 
epidermal cells only. 
A microscopical examination of the brown spots revealed the presence of a 
granular brownish substance and of a great accumulation of typical starch grains. 
Such starch grains were few or absent in the surrounding epidermal cells; also 
they did not occur in the normal dark purple or crimson spots. The brown sub- 
stance is almost certainly a decomposition product of anthocyanin, the normal 
colouring matter. Dr F. W. Bews, Professor of Botany, Natal University College, 
has suggested that possibly the starch also is to be regarded as a decomposition 
product of the anthocyanin : but the great abundance of the starch somewhat 
militates against this view. 
The brown substance is insoluble in alcohol, ether, HCl (50 '/q) and potash 
(1 %). 
With the naked eye there is a sharp discontinuity between white flowers with 
purple spots and white flowers with brown spots. Microscopical examination, 
however, shows that the discontinuity is not really so sharjDly defined. In many 
of the coloured cells of the purple spots traces of the brown substance may be 
detected, and at first it was thought possible that the removal of the purple colouring 
substance with alcohol would leave brown spots. This, however, was found not 
to be the case. Only rarely is the brown substance in sufficient quantity to mark 
out the spot on the removal of the anthocyanin. The point to notice is that brownish 
purple spots intermediate between the normal purple spots and the brown spots 
are only rarely found. Traces of an intermediate condition can be found micro- 
scopically, but there appears to be normally a gap between a small amount of 
decomposition product and total decomposition. 
It will be remembered that there occurs a similar gap between ordinary foxgloves 
and crowned foxgloves; intermediate conditions are possible but only rarely 
occur. 
