120 FAMILIES OF FLOWERING PLANTS 
Everyone who has penetrated a bog filled with sphagnum moss has 
noticed, the glistening reddish-hued leaves of the round-leaved sundew 
(Drosera rotundifolia), which is our commonest species. Its tiny white 
flowers open singly, and the curved one-sided raceme elongates just 
sufficiently to enable the flower of the day to point skyward. D. filifor- 
mis, with long slender leaves and rose- 
purple flowers, common in the New 
Jersey pine barrens and southward, 
is a more handsome plant (see Fig. 
104). An examination of the leaves of 
Drosera under a lens will show a mi- 
nute drop of viscid fluid at the tip of 
each hair; this serves to entangle small 
flies, gnats, etc. In Dionaea, however, 
the process of specialization has gone 
# even farther, and the leaf, which is 
y divided at the midrib into two nearly 
semicircular fringed lobes, closes like 
a steel trap the moment any foreign 
object comes in contact with the slen- 
der sensitive hairs of its inner surface. 
After the imprisoned object is thor- 
: . oughly digested, the leaves again ex- 
ess Oa en Absecon: re ease pand; if a bit of wood or other useless 
Tl BL Northeast U.S: material has been imprisoned, they 
will open in a few hours. 
CHAPTER XXI. 
Order Rosales. 
This large and important order, of which the Rose family (Rosa- 
ceae) is the type, contains seventeen other families, including the Pa- 
pilionaceae, Mimosaceae, and Caesalpiniaceae, three groups which col- 
lectively comprised the old order Leguminosae, and which include the 
most valuable of our economic plants. In so large a group as the 
Rosales, it is difficult to find distinguishing characters which will applv 
equally well to all the members; but in general the roseworts may be 
known by the insertion of the stamens, which may be either hypogynous 
(on the axil below the pistil) or epigynous (on the pistil itself); by the 
sepals, which are more or less united or confluent with the receptacle; 
and by the simple ovary, consisting of one or many distinct or united 
carpels. 
Family Podostemaceae. River-weed Family. Contains about 21 
genera and 175 species, all tropical except Podostemon, which is repre- 
