SECTION 7.] 



ORDINARY LEAVES. 



61 



so that what would be the upper surface is within, and all grown together, 

 except next the bottom, where each leaf covers the next younger one. It 

 was from their straddliug over each other, like a man on horseback (as is 

 seen in the cross-section, Fig. 165), that Linuaeus, with his lively fancy, 

 called these Equitant leaves. 



161. Leaves with no distinction of Petiole and Blade. The leaves 

 of Iris just mentioued show one form of this. The flat but narrow leaves 

 of Jonquils, Daffodils, and the cylindrical leaf of Onions 

 are other instances. Needle-shaped leaves, like those of 

 the Pine, Larch, and Spruce, and the awl-shaped as well 

 as the scale-shaped leaves of Junipers, Red Cedar, and 

 Arbor-Vitae (Fig. 166), are examples. 



162. Phyllodia. Sometimes an expanded petiole takes 

 the place of the blade ; as in numerous New Holland 

 Acacias, some of which are now common in greenhouses. 

 Such counterfeit blades are called phyllodia, meaning 

 leaf-like bodies. They may be known from true blades 

 by their standing edgewise, their margins being directed 

 upwards and downwards ; while in true blades the faces 

 look upwards and downwards ; excepting in equitant 

 leaves, as already explained. 



163. Falsely Vertical Leaves. These are apparent 

 exceptions to the rule, the blade standing edgewise in- 

 stead of flatwise to the stem ; but this position comes 



by a twist of the stalk or the base of the 

 blade. Such leaves present the two 

 faces about equally to the light. The 

 Compass-plant (Silphium laciniatum) is 

 an example. So also the leaves of Bolto- 

 nia, of Wild Lettuce, and of a vast num- 

 ber of Australian Myrtaceous shrubs 

 and trees, which much resemble the 

 phyllodia of the Acacias of the same 

 country. They are familiar in Calliste- 

 mon, the Bottle-brush Flower, and in 

 Eucalyptus. But in the latter the 

 leaves of the young tree have the nor- 

 mal structure and position. 



164. Cladophylla, meaning branch- 

 leaves. The foliage of Ruscus (the Butcher's Broom of Europe) and of 

 Myrsiphyllum of South Africa (cultivated for decoration under the false 



Fig. 166. Branch of Arbor-Vitae, with awl-shaped and scale-shaped leaves. 

 Fig. 167. The ambiguous leaf ? (cladophyllum) of Myrsiphyllum. 

 Fig. 168. Same of Ruscus, or Butcher's Broom. 



