40 



PART I. MORPHOLOGY. 



[12 



possess a well-developed lamina, which presents the various pecu- 

 liarities of conformation previously described. 



The texture of the leaf is dependent upon the mode and duration 

 of its existence. The texture of most leaves may be described as 

 herbaceous. Leaves of this kind last usually for only a single 

 season, and die or fall off in the autumn. Leaves of firmer .texture, 



which are said to be cori- 

 aceous, survive the winter, 

 and either fall off when 

 the new leaves are de- 

 veloped (the Privet), or 

 continue to live for several 

 years (Holly, Box, and 

 most Conifers) ; the acicu- 

 lar leaves of the latter 

 may persist for as many 

 as twelve years (Silver 

 Fir). Fleshy or succulent 

 leaves occur in plants in- 

 habiting dry regions or 

 positions, such as Aloe, 

 Sedum, etc. 



It is worthy of note 

 that foliage-leaves of dif- 

 ferent form sometimes 

 occur on the same shoot. 

 For instance, it is com- 

 monly the case that the 

 first leaves of young 

 plants are of a form dif- 

 ferent from, and usually 

 simpler than, that of those 

 which are subsequently 



P roduced > and exhibit a 



greater resemblance to 



fhn^P nf nlliVrl nlanfa 

 jn Se O1 alliea plants. 



Thus, Eucalyptus Globu- 

 lus has at first oval dorsiventral leaves, and subsequently elon- 

 gated isobilateral leaves. Again, the primary leaves or cotyledons, 

 when they develope into foliage-leaves, are always different in 

 form from the subsequently developed foliage-leaves, being much 



region; L region of the foliage-leaves; H hypso- 



phyllary region ; d the bracts i b the flowers in 

 their axils ; roots. 



