1897 ] BRIEFER ARTICLES 195 
definite course of evolution in the marking of the under side of the 
ray also. For on the under side the brown appears first in the thinner 
portions of the ray, and last on the thick veins. It is as though the 
brownish pigments were spread first over the upper surface and sub- 
sequently increased in depth, first showing through in the thin areas. 
Precisely the same series was later constructed from blossoms of 
the commercial Freesia refracta alba grown in our greenhouses. In 
this case we have a reversion from the highly selected white type. But 
the appearance of an orange yellow spot at the base of the upper petal 
and its extension over first the inner surface, and secondly its appear- 
ance on the backs of the petals, followed the same definite lines as 
those already studied in Coreopsis tinctoria. In this case sections were 
made through petals from various blossoms in the series. In the first 
appearance of yellow pigment it was confined to a single layer of sub- 
epidermal cells, and was from here subsequently propagated through 
the intermediate cells to the under surface of the petals. 
This centrifugal encroachment of a darker upon a lighter color in 
blossoms is one of the commonest lines of definite variation. In 
Lepachys columnaris Torr. and Gray it gives the variety pudcherrima 
Torr. and Gray. In the florists’ Primula Chinensis it gives the beauti- 
ful “Schwarzaugen” varieties of late German catalogues. With more 
or fewer exceptions the same method governs the variations in mark- 
ings of marigolds, perenne Ceait a de pelargoniums, irises, 
and dozens of other sp g which will readily occur to the 
gardener. 
It is quite remarkable that any given lot of variations should hap- 
pen to fall into one continuous series; and this becomes of still 
-gteater importance when found to hold true with groups of highly 
cultivated and severely selected plants, like the Coreopsis and Freesia 
cited. It is no longer final to” say that variations “‘are as definite as 
Le ad oo in environment are, which determine and control their 
