No. 423.] NORTHERN POLYPETALOUS FLOWERS. 217 
which do not restrict themselves to flowers, were observed on 
red and blue blossoms. Due consideration should. be given to 
the limitation of the visits of flies by the form of the corolla, 
by scent, by the acuteness of the species in finding the honey, 
as well as by its adaptations and habits, and to the fact that in 
the case of several families the above conclusions are based on 
comparatively few observations.: . 
Chrysoplenium alternifolium has no petals, but the sepals are 
bright yellow and the disk is also yellowish. | Like the species 
of Saxifraga, it is visited chiefly by flies. The petals of Par- 
nassia are white, with greenish veins. |. palustris is described 
as a “deceptive flower.” It contains numerous yellow glandular 
bodies which appear like minute drops of honey, by which flies, 
especially Syrphidze, are deceived. The flower contains a small 
amount of honey. In Hydrangea the cyme is made conspicuous 
by the enlargement of the calyx of the marginal flowers. In 
H. hortensia, cultivated from eastern Asia, the flowers are nearly 
all neutral and enlarged, and at first are green, changing directly 
to pink or purple. “The variable character of Hydrangea 
flowers," says a writer in the Journal of Horticulture, “when the 
plant is grown under certain conditions, has for many years 
been a sort of horticultural puzzle, which is still far from being 
satisfactorily solved. Plants with bright pink flowers, and those 
with flowers of a tolerably good blue, are not infrequently met 
with in positions near each other and apparently in soils exactly 
alike." A change of color in the flowers from pink to blue is 
sometimes caused by a change of soil, as the removal of a plant 
from a peaty soil to one of opposite character. The addition of 
iron to the soil frequently appears to produce the desired color 
change, though time is always required, the blué coloring not 
developing until the second year. Saxifraga pennsylvanica and 
Heuchera americana have green petals. Several species of 
Saxifraga are proterogynous, and the flowers in passing from 
the female to the male stage increase greatly in size. 
The Grossulariaceze (gooseberry family) contain only a pe 
genus, Ribes. Of the northern species four are green, six white, 
one yellow, and two'greenish purple. — o of the species are 
greenish in part. In“ Ribes. lpi th e flowers are green 

