FAMILIES OF PLANTS 
91 
EVENING-PRIMROSE FAMILY (ONAGRACEAE) 
A rather large family which contains many plants with showy 
flowers. The ovary is entirely below the other parts of the flower, 
and there are usually 4 sepals, 4 petals, 8 stamens, and 1 style. In 
many members of the family the flowers open at about sundown and 
are pollinated by night-flying insects, principally moths. The fruit 
is a dry capsule. 
1. Seeds with a tuft of hairs at the tip. 2. 
1. Seeds without a tuft of hairs at the tip. 3. 
2. Flowers large. Fireweed ( Chamaenerion )______ (p. 91) 
2. Flowers small. Willow-weed ( Epilobium )-(p. 91) 
3. Leaves all basal. 4. 
3. Leaves not all basal. 5. 
4. Stigma deeply 4-lobed. Moonrose ( Pachylophus )_(p. 92) 
4. Stigma entire or nearly so. Taraxia ___(p. 92) 
5. Flowers very small. Gayophytum _ _(p. 92) 
5. Flowers nearly a half inch long or longer. 6. 
6. Stigma entire or nearly so. Gaura parviflora _(p. 92) 
6, Stigma deeply 4-lobed. 7. 
7. Flowers yellow. Onagra strigosa _(p. 93) 
7. Flowers white. Sweet evening-primrose ( Anogra nuttallii )-(p. 93) 
Fireweed (Chamaenerion angustif olium) .—A perennial herb 
growing 1 to 5 feet high and producing large numbers of scar¬ 
let to purple flowers. It is very common in the park and when 
in full bloom is one of the most beautiful and conspicuous of the park 
flowers. The leaves are lance-shaped and nearly entire. The young 
buds hang downward, but they straighten up as they mature. The 
corolla is slightly irregular, and the eight stamens mature succes¬ 
sively, one at a time. The four-lobed stigma does not open up and 
become ready to receive pollen until all of the stamens have shed 
their pollen. By this means cross pollination is practically assured. 
The mature capsules are 2 or 8 inches long, and the seeds are 
provided with long, whitish hairs which make them well adapted to 
being blown about by the wind. 
Chamaenerion latif olium is a smaller plant with fewer but some¬ 
what larger flowers and broader leaves. It is not common. 
Willow-weed {Epilobium ).—The willow-weed is a slender plant 
closely related to the fireweed and resembling that plant, except that 
its flowers are very much smaller and so much less conspicuous. The 
flowers may be lilac, violet, pink, rose, white, or cream color. It is 
easily recognized, but the different species are often very difficult to 
distinguish. The following species have been identified in the park; 
Epilobium adenocaulon 
Epilobium alpinum 
Epilobium anagallidif olium 
Epilobium clavatum 
Epilobium drummondii 
Epilobium hornemannii 
Epilobium ovatifolium 
Epilobium paniculatum 
Epilobium p&rplexans 
Epilobium suffruticosum 
