KEY TO FEOWERING PLANTS 
307 
KEY TO THE PRINCIPAL GROUPS OF PLANTS 
1. Plants without distinction of root, stem, and leaf; no flowers (green 
scum, water weeds, fungi, etc.) 
1. THALLOPHYTA 
1. Plants with distinct Ivs., with or without roots or fls. 
2. EMBRYOPHYTA 2 
2. Small plants (to 1 dm. tall) with green Ivs.; or scalelike growths on 
earth; or floating; without true roots or fls. (Mosses, etc.) 
1. ATRACHEATA 
2. Plants with true roots and vascular bundles; mostly with veiny Ivs. 
2. TRACHEATA 3 
3. Plants without fls.; herbs, propagated by spores 4 
3. Plants with fls. (stamens and pistils), propagated by seeds 5 
4. Spores yellow; Ivs. small; one sporangium in each axil 
2.1. LYCOPSIDA 
1. LYCOPODIALES 
4. Spores green, cottony, borne in terminal cones; stems jointed 
2.1. LYCOPSIDA 
2. EQUISETALES 
4. Spores borne on the backs of ordinary or modified Ivs. 
2.2. PTEROPSIDA 
1. ASPERM^ 
5. Trees with light grey bark, and 2-lobed Ivs. with fine, forked, parallel 
vein^ 
2.2. PTEROPSIDA 
2. GYMNOSPERM^ 
5. GINKGOALES 
5. Trees or shrubs with conelike fls., and needle-like, mostly evergreen 
2.2. PTEROPSIDA 
2. gymnosperm;e 
6. CONIFERALES 
Si. Trees, shrubs, or herbs with true fls., and seeds borne in an ovary. 
Pollen received on a stigma* PTEROPSIDA 
3. ANGIOSPERM^ 6 
6. Fls. usually with their parts in 5’s; Ivs. net-veined; stems with cen- 
tral pith, surrounded by a ring of wood, or vascular bundles, with 
growth in thickness by means of cambium; cotyledons 2. 
' 2.2.3.I. DICOT YLEDONE^ 
6. Fls. usually with their parts in 3’s; Ivs. parallel-veined; vascular 
bundles scattered about in stems, without growth in thickness 
(cambium) ; cotyledon 1. All herbs except 1 prickly woody vine. 
• 2.2.3.2. MONOCOTYLEDONE^ 
* “Double flowers” must usually be identified by means of their single 
prototypes. Where doubling is due to change of stamens into petals, the 
key may be used by counting the inner petals as stamens. 
