306 INTRODUCTION TO BOTANY 
which many asexual spores are formed. In both reproductive 
and nutritive work the bryophytes are much more complex 
than the thallophytes. 
The ferns have woody tissue and often have immense leaves 
and are well equipped to do chlorophyll work. They often 
store in one year food which serves in part for the growth of 
the next year. Asexual spores are formed in great numbers 
by means of highly specialized sporangia. These spores, when 
they germinate (as in the case of the ferns studied), produce 
chlorophyll-bearing, independent plants, which grow in obscure 
places and produce sex organs by means of which sex spores 
are formed. From the odspores new leafy fern plants grow. 
In the spermatophytes we have the most important’ and 
most prominent plants of the earth. They have vegetative 
structures that are very much more complex than are those 
of any of the preceding groups. These vegetative structures 
are so widely differentiated as to meet the demands of almost 
any conditions. The flower and the seed are special reproduc- 
tive structures which, with successful vegetative structures, 
seem to have given these plants their position of ascendancy 
in modern plant life. 
291. Classification. Throughout this book many illustra- 
tions of the seed-plant group of the plant kingdom have been 
used. Although but a few of these illustrations are cited 
here, enough are given to enable the student to relate the 
classification of spermatophytes to that of preceding groups. 
Group D. SPERMATOPHYTES 
Cass J. Gymnosrerms. Genera used as illustrations — Pinus (pine), 
Picea (spruce), Juniperus (juniper), Sequoia (“big trees” and 
redwoods) 
Ciass IT. ANGIosPpERMS 
Sus-cLass I. Monocoryiepons. Genera used as illustrations — 
Lilium (lily), Zea (corn), Triticum (wheat), Avena (oats), and 
many others 
Sun-ciass II. Dicotyrepons. Genera used as illustrations — 
Quercus (oak), Capsella (shepherd’s-purse), Pyrus (apple and 
pear), Rosa (rose), and many others 
