No. 423.] NORTHERN POLYPETALOUS. FLOWERS. 233 
metallicum, from Central America, has magnificent leaves, purple 
beneath and metallic blue above. 
In the Onagracez, or evening primrose family, there are three 
green, fourteen white, twenty-four yellow, ten red, and six purple 
flowers. The three small green flowers belong to Ludwigia, 
and the petals are either minute or absent. Many of the white 
flowers show a tendency to change to pink or red. The large 
white flowers of the three northern species of Anogra all turn 
pink with age. Several species of Gaura also change to red. 
G. coccinea is red, turning scarlet in fading. The two species 
of Circæa (enchanter’s nightshade) are delicate, colorless little 
plants, , which grow in damp, shady woods and have small white 
flowers, fertilized by flies. The yellow flowers are in part diurnal 
and in part nocturnal as in Onagra biennis. Yellow is a much 
rarer color than white in flowers expanding at night. 
With a single exception the flowers of Epilobium are red or 
red purple. Æ. angustifolium, called **fireweed " (as the plants 
spring up in abundance in newly cleared or burnt lands), has 
very conspicuous flowers in long, terminal racemes. The sepals 
and petals are purple red, except the lower sepal, which is white, 
and rarely the whole flower reverts to white. The pollen is 
greenish purple, and the stems and seed vessels are purple. 
Honey is secreted by a green, fleshy ring at the base of the 
style. Bumblebees are the most important agents in intercross- 
ing and will visit as many as thirty-seven flowers in a minute. 
I have collected on this species twenty-one Hymenoptera, five 
Diptera, three Lepidoptera, and two beetles. In the smaller 
species of Epilobium, such as E. palustre and E. lineare, the 
small flowers are reddish or white, both kinds occurring on the 
same plant. When the stems are purple the flowers are more 
often red than when the stems are green. There are few vis- 
itors, and self-fertilization regularly occurs. The only northern 
white species of Epilobium is Æ. a/Pigum, which has small 
white flowers which are regularly self-fertilized. In Æ. %irsu- 
tum the four white stigma lobes form a cross on the red field 
of the petals. 
The exotic genera deserve special mention. In Zofezza 
racemosa, from Mexico, there are on two of the petals dry, 
