298 INTRODUCTION TO BOTANY 
thousand species, and some think this number too low. Added 
to this fact of the large number of species is the fact that the 
number of individuals of a species may often be enormous, as 
in the common blue grass, oats, or corn, each species of which 
consists of unknown millions of individual plants. 
The diversity of angiosperms in chemical composition is 
equally great. Some constitute our most important foods, 
others produce a large part of our medicines, and others 
produce substances so poisonous that they are feared by all 
who know about them. 
282. Vegetative structures. The essential facts regarding 
the ways in which angiosperms make and use their food mate- 
rial have already been given (Chapter IJ and the followmg 
chapters). There have also been abundant discussions to show 
something of the variety of structures that plants of this group 
exhibit when they grow under different circumstances, as in 
the water, on especially dry land, and under extremes of tem- 
perature. The ways in which different vegetative structures 
are used as means of reproduction are presented in chapters 
on roots, stems, leaves, etc. Reproduction by means of flowers 
has also received some attention, but a further discussion at 
this time will serve to connect the angiosperms with the pre- 
ceding groups. 
283. The angiosperm flower. The name flower is some- 
times used in speaking of the collections of sporophylls that 
are seen in the cones of pines. In the angiosperms, in addi- 
tion to sporophylls, there are usually other lcaf-like organs 
around the sporophylls, and the presence of these additional 
floral leaves is popularly considered as essential to the flower 
(figs. 9and 102). These added floral leaves are usually colored, 
often in very striking ways. There are angiosperm flowers 
that do not have these added floral leaves, such flowers being 
naked (liv. 104). No complete distinction can be made be- 
tween the collection of sporophylls, which in the pines was 
called a strobilus, and the collection which is commonly known 
as a flower in the angiosperms. 
