4 Using the Key and Flora. 



we find two large groups, one having " flowers monoecious or dioecious, stami- 

 nate and sometimes pistillate, flowers in catkins," and the other having 

 " flowers not in catkins." The maple, of course, belongs under the latter. 

 Here we find two main groups, headed, "Pistil more than I," etc., and 

 "Pistil I," etc. Our plant belongs under the latter, where the plants are 

 grouped as " herbs," or " shrubs and trees." The maple being a tree, we 

 proceed under the latter heading. 



The maple has a pair of ovules in each cell of the ovary, and the fruit is a 

 double samara, and we accordingly find th*at we must look for it in the genus 

 Acer, in the family Sapindaceae, on page 74. Having traced a plant to its 

 family (in this case the Key directed us at once to the genus), it is a good 

 plan to read the description of the family, to make certain that the plant has 

 been rightly traced. Now read the description of the genus, Acer, and of the 

 species under it, and determine to which one of these our maple belongs. 



As a final example we will trace the single-flowered Sweet Alyssum of the 

 greenhouses. Beginning with the Key on page 7, as oefore, we find our 

 plant goes to Subclass II., and under this to division B on page 8. Under B 

 we find three main groups, numbered (i), (2), and (3), depending on the 

 number of stamens. Our plant must be under (3), " Stamens not more than 

 twice as many as the petals," etc. Under this division we find two chief 

 groups, designated by (a), "Ovary superior," etc., and (), "Ovary inferior," 

 etc. (on page 10). Clearly our plant comes under (#). Here we find four 

 groups, depending on the number and character of the pistils. Our plant 

 goes to the last of these, "Pistil I, compound, as shown by the number of 

 cells, placentae, styles, or stigmas." (Read about compound pistils on pages 

 203 and 204 of the Botany.) 



In alyssum we conclude that two carpels compose the pistil, because there 

 are two cells, each having a row of ovules; thus indicating two placentae and 

 two carpels. A pistil may be one-celled and still be compound as indicated 

 by the placentae or rows of ovules. The violets afford a good example of this. 



Under " Pistil I, compound," etc., there are two groups, one having the 

 " ovary I -celled," and the other with "ovaries 2 or more celled." Our plant 

 comes under the latter, and under " Flowers nearly or quite regular " ; and 

 since the stamens of alyssum are tetradynamous, we find that we must look 

 for it under the family Cruciferae, page 47. 



Following the Key to the family, we find we are led to Division II, under 

 " Flowers, white " ; and since the pods of our plant become orbicular, we are 

 taken to Genus XIV, Alyssum, We now turn the pages of the family until 

 we find this genus (on page 53). 



When only a few genera have been given under a family, a key to the 

 family is not given, and the proper genus is to be determined by reading the 

 description of each under that family. 



To understand the significance of the accent marks used with the names 

 of the families, genera, and species, read the footnote on page 12. 



This Spring Flora does not pretend to be complete for any region. Its 

 purpose is to afford the student sufficient drill during the spring term to make 

 him thereafter independent in the use of the larger Floras. The habit of 

 looking up the names of plants leads incidentally to a knowledge of many 

 interesting facts about plant structures and relationships. 



