No. 423.] NORTHERN POLYPETALOUS FLOWERS. 223 
central flowers contrast with an older outer ring of rose-colored 
flowers. In the yellow clover the newer flowers contrast with a 
ring of chestnut brown. In Vicia cracca the older flowers bend 
downward and turn from violet blue to dark purple; while the 
purple flowers of Desmodium become green in withering. 
Striking color contrasts are also presented by the individual 
flower. The wings of the white corolla of Vicia faba (bean) 
are marked with two black eye-spots, and in the sweet pea and 
cultivated lupines the combinations of color are innumerable. 
Astragalus vesicarius has yellow blossoms in the Tyrol but 
violet on the limestone mountains of Hungary. 
Nine families belong to the order Geraniales. In the genus 
Geranium of the Geraniacez the larger and more conspicuous 
purple flowers are visited abundantly by insects and have nearly 
or quite lost the power of self-fertilization. The smaller flowers 
are paler or white, attract few insects, and self-fertilization regu- 
larly takes place. Geranium pratense has been seen to produce 
on the same plant, when cultivated in a garden, both white and 
blue flowers. G. robertianum, or red robin, has ribbed red- 
purple petals and, "notwithstanding its disagreeable odor, is 
sought by bees as well as flies and beetles. In the pink flowers 
of Erodium cicutarium the upper petals are marked with dark 
lines, which serve as pathfinders. According to a series of 
forms figured by Knuth these markings vary greatly, from a 
few lines to spots and markings on all five petals? In the genus 
Pelargonium from the Cape of Good Hope, this office of the 
upper petals becomes very highly developed; P. tricolor has the 
three lower petals white and the two upper crimson, each with 
a dark spot at base. The flowers of the Geranium always turn 
towards the sun. 4 
Most of the northern species of Oxalis of the Oxalidacez are 
yellow and possess an acid juice, but O. acetosella, which grows 
in open woodlands, has large, pretty white flowers, veined with 
pink. It is sometimes called * wood sour,” as druggists obtain 
from it salt of lemons. The plant is of social habit, and the 
flowers are quite conspicuous, yet are rarely visited nd flies, 
lDarwin. Animals and Plants under Domestication, vol. i, p- 404- 
2Knuth. Handbuch der Blutenbiologie, Bd. i, p. 1 
