232 THE AMERICAN NATURALIST. [VoL. XXXVI. 
the flowers are white or yellowish; in Opuntia yellow, or in 
O. opuntia and O. humifusa yellow with a reddish center; in 
Cereus in the nocturnal. forms white, in the diurnal species red 
or crimson; in Echinocactus yellow, white, and crimson; in 
Mamillaria yellow, pink, white, and purple; and in Anhalonia 
white, rose, and purple. The spines of the Cacti are often very 
beautiful objects and exhibit a great variety of color, as white, 
black, yellow, red, and purple. The stems, while usually green, 
are frequently nearly blue; the fruits are green, red, and purple. 
The Thymeleacez and Eleagnacez in the northern states 
have no petals, but the calyx is v; enlarged; prolonged into a tube, 
and colored yellow, red purple, or white. In Europe Daphne 
mezereum has the red-purple flowers visited by long-tongued 
bees, flies, and butterflies ; in the Alps the white or red flowers 
of D. striata are strong scented in the evening and are visited 
by moths. — 
The petals are wanting in the single green species of the 
Lythracez, or loosestrife family, Didiplis diandra, which has 
minute solitary flowers. The loss of the corolla is doubtless 
due to retrogression. In Ammannia the flowers are small and 
the purple petals fall away as soon as they expand, and in the 
southern A. latifolia they are wanting. The purple flowers of 
Lythrum vary from small to large. The eighteen possible ways 
of fertilization in the red-purple trimorphous flowers of Lythrum 
salicaria were made the subject of a long series of laborious 
experiments by Darwin, which resulted in breaking down the 
last barrier between species and varieties. It is a singular fact 
that the pollen of the longest stamens in this species is green, 
and of the middle-sized and shortest, yellow. The legitimate 
fertilizers are long-tongued insects. In Parsonia, or Cuphea as 
it is better known, the flowers are pink or crimson, and i in a cul- 
tivated species from Mexico, C. platycentra, there are no petals, 
but the tubular calyx is bright vermilion with a violet border. 
The Melastomacez are represented in North America only 
by the genus ; Rhexia, with handsome purple or yellow flowers. 
The fma is most abundant in South America. In Heeria 
a part of the stamens are devoted to rendering the flowers 
conspicuous and a pen to producing pollen. - Cyanophyllum 


