No. dtr.) NORTHERN APETALOUS FLOWERS. 203 
The order of Urticales does not show any advance in the 
structure of its flowers over the Fagales. The order is a 
large one, comprising some fifteen hundred species, distributed 
chiefly through tropical regions. The flowers are small, in 
inconspicuous spicate or axillary clusters, greenish, and ane- 
mophilous. In Ulmus (elm), of the Ulmaceze, the flowers are a 
reddish-purple, and the wood of U. fulva is reddish also. The 
Moracee, mulberry family, is composed of trees and shrubs 
with milky juice. The flowers are greenish, but in lieri 
the calyx or receptacle becomes fleshy and bright-colored ; 
Morus, red-purple and white; in Toxylon, ps elidel 
and in Broussonetia the drupes are red. Of the tropical genus 
Ficus there are six hundred species, three of which occur 
in the Southern States. Its manner of fertilization has been 
the subject of much discussion. The hollow, pear-shaped 
receptacle is lined with male and female flowers, and pollina- 
tion is effected by small wasps, which force their way into the 
cavity forthe purpose of depositing their eggs. In fruit the 
enlarged receptacle becomes deep purple, purplish-red, orange, 
yellow, and whitish, and is eagerly devoured by birds, espe- 
cially parrots. The greenish fruiting bracts and achenes of 
— lupulus (hop) bear numerous yellow glands from z§5 
to 4l, inch in diameter. When fresh they are filled with a 
yellow liquid containing wax and resins and a bitter- tonic 
medicinal principle called /upu/im. About one ounce may be 
obtained from one pound of hops. These glands doubtless 
protect the flowers from attacks of aphides. Glandular-leaved 
peach and nectarine trees are less subject to curl, to mildew, 
and to the attacks of aphides than the non-glandular (Darwin, 
Animals and Plants under Domestication, Vol. I, p. 364). The 
hop in some years is attacked by vast numbers of Aphis humuli, 
and is also subject to blight from a parasitic fungus. The 
flowers of the nettle family are green, wind-fertilized, and the 
pollen is scattered by the explosion of the anthers. 
The order Santalales includes about seven hundred and fifty 
species, which are most abundant in tropical regions, only six 
species being found in the Northern States. The two northern 
species of the Loranthaceæ, mistletoe family, are parasitic 
