192 



HOW TO STUDY PLANTS. 



[LESSON 32. 



page xvii, the student, seeing at once that the plant belongs to the 

 Phosnogamous series, proceeds to determine the class. The netted- 

 veined leaves would seem to refer the plant to the first class ; while 

 the blossom (Fig. 366, 367), constructed on the number three, natu- 

 rally directs us to the second class, in which this number almost uni- 

 versally prevails. Here the student will be somewhat puzzled. If the 

 seeds were ripe, they might be examined, to see whether the embryo 

 has one cotyledon only, or a pair. But the seeds are not to be had 

 in spring. We must judge, therefore, by the structure of the stem. 



Is it exogenous or endogenous ? If 

 we cut the stem through, or take off 

 a thin slice crosswise and lengthwise, 

 we shall perceive that the woody 

 matter in it consists of a number of 

 threads, interspersed throughout the 

 soft cellular part without regularity, 

 and not collected into a ring or layer. 

 In fact, it is just like the Corn-stalk 

 (Fig. 351), except that the woody 

 threads are fewer. It is therefore endogenous (422) ; and this 

 decides the question in favor of Class II. MONOCOTYLEDONOUS or 

 ENDOGENOUS PLANTS (page xxiii), notwithstanding the branching 



veins of the leaves. For neither this character, 

 nor the number of parts in the plan of the blos- 

 som, holds good universally, while the plan of the 

 stem holds without exception. 



559. The first division of this class, in the Ar- 

 tificial Key, is into three sections, marked A, B, 

 and C. Our plant plainly belongs to section B, 

 the only one in which the flowers exhibit both a calyx and a corolla. 



560. Under this are two subdivisions, marked 1 and 2. The 

 plant we are examining belongs to the second, having solitary (i. e. 

 single) flowers. This again is subdivided into two sections, the first 

 with a single star prefixed, the second with two stars. Having the 

 "perianth free from the ovary" our plant falls into the second (page 

 xxiv, line 2). 



561. At the next step we have four subdivisions to select from, 

 marked by daggers (-): the three herbaceous sepals and three 



367 



FIG. 366. Flower of Trillium erertum, viewed from aliave. ?' 1. Diatrrnm of the same; 

 a cross-section of the unopened blossom, showing the number and arrangement of parts. 



