ILLINOIS NATURAL HISTORY SURVEY MANUAL 1 
naked stem, bearing several pretty violet flowers. We examine 
the flowers and find 5 green sepals, 5 violet petals, 10 stamens, 
an unlobed ovary and § styles. We will not pick any of the 
flowers but will sit down among them with our book and turn 
to the Key to Families, page 30. 
TRACING THROUGH KEY TO FAMILIES 
Starting with number 1 in the key, we have a choice of three 
groups of characteristics: “Trees or shrubs, erect,” “Shrubs 
(vines) that climb,” and “Herbs.” We choose “Herbs” and go 
to the number given, which is 19. At 19 we find a choice of four 
alternatives, and since the leaves of the plant we have are not 
abnormal in that they are not curiously shaped and are not 
scales or spines, we go on as indicated to the number 20. Our 
plant does not have milky sap, and so we proceed to 22; from 
there, since its leaves are netted veined, we go to 23. As there is a 
corolla we go to 24, furthermore the petals are separate, and 
sO we go to 32. At 32 we have “Corolla borne on the receptacle” 
and “Corolla borne on the calyx.”’ Choosing the first, we move on 
to 33, and from there, since the leaves are not fleshy, we go to 
35. Our plant is growing on land, so that we go on to the next 
choice at 36, from which we jump to 41, since the flower has, 
as we have said, 10 stamens. Here the fact that the flower is 
perfect sends us to 42, and thence, since the corolla is regular, 
to 43. Here the 5 violet petals of our flower make us choose 
“Petals 5” and we go as directed to 45. Here we examine the 
ovary again, find it not 5-lobed, and go on to 46. Now we must 
be careful in picking out the line which really describes the 
leaves of our plant—are they opposite, alternate or basal? The 
key makes it as easy as possible here, limiting the choice to 
two, and since we saw in the beginning that our plant had basal 
leaves, we conclude that we have found some member of the 
Wood Sorrel family. Turning to page 175 we find this family 
begun with a description of the violet wood sorrel, which, as we 
read, proves to be the plant we have been tracing. 
USE OF KEY TO GENERA 
On some occasions we may have quite a few descriptions 
within the family to run through before we can be sure of our 
plant, and a little more help would be welcome. Let us take 
such an example, leading through a new set of signposts in the 
key. Suppose that on a little later trip, just outside the woods 
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