54 



HOW PLANTS GROW. 



152. Stipules, as already explained (120), are a pair of appendages at the base of 

 the leaf, one on each side. These often grow fast to the base of the leafstalk, 



as they do in the Rose and in Clover (Fig. 136 ; st, 

 the stipules). Or they may join with each other and 

 form a kind of sheath round the stem, as they do in 

 the Buttonwood and in Polygonum (Fig. 137). 

 Many leaves have no stipules at all. In many 

 cases they fall off very early, especially those that 

 serve for bud-scales, as in Magnolia. 

 153. The Arrangement of leaves on the stem has 



already been explained as to the two principal veays 

 (59). Leaves are either 



Alternate, when they follow each other one by one, 

 as in the Morning-Glory (B'ig. 4) and the Linden 

 (Fig. 83) ; or 



Opposite, wlien in pairs, 

 that is, two on each joint of 

 stem, one opposite the other, 

 as in Maples (Fig. 84). To 

 these may be added a third, 

 but less common arrangement, 

 viz. the 



Whorled ; where there are 

 three, four, or more leaves on 

 Stipule, uniieii. \)^Q Same joint of stem, forming 



a circle or whorl ; as in Madder and Bedstraw (Fig. 137'). But tliis is only a 

 variety of the opposite mode. 



137' 

 Whorled leaves. 



Analysis of the Section. 



81. Vegetation very simple in plan, very diversified in particulars. 82. The study of the forms of 

 the organs is Morphology. 



83-89. Eoots, their forms and kinds. 84. Primary or original; secondary; hoiv they originate. 

 85. Aerial roots. 86. Aerial rootlets. 87. Air-Plants ; how they live. 88. Parasitic Plants, their 

 economy. 89. Shapes of roots : fibrous ; fleshy ; the principal sorts. 



90. Forms or kinds of stem ; herbaceous, shrubby, arboreous. 91. Culm or straw-stem. 92. Direc- 

 tions or positions of stems. 93. Peculiar sorts. 94. Thorns or Spines, how shown to be branches ; 



