LEA VES. 25 



LESSON V. 

 LEAVES. 



Leaves are organs of (1) respiration, (2) evaporation, and 

 (3) assimilation; for most plants breathe through them, 

 absorbing carbon and other elements of plant food. The 

 general application of the word ' leaf ' is well understood ; 

 but it must be borne in mind that in a botanical sense the 

 word is not only applied to the foliage leaves, which are 

 mostly green, but also to the flower leaves ox petals, which 

 are generally coloured. Leaves greatly vary in size. Some 

 are only a small fraction of an inch long, and no wider than 

 a thread. Others are from thirty to forty feet in length — 

 the latter enormous size having been attained by the leaf of 

 a sago palm in the Royal Gardens at Kew. The magnifi- 

 cent shield -like leaves of the Victoria Regia or Royal 

 water-lily sometimes measure from five to six feet across. 

 A specimen of this plant may be seen in the Melbourne 

 and the Adelaide Botanic Gardens. The leaves of some 

 of the Australian fan palms are sufficiently broad to protect 

 one from a shower of rain. 



The leaves of some plants decay and fall in autumn, and 

 are replaced by a fresh crop in the following spring. Such 

 plants are called deciduous or ' leaf-shedders.' The British 

 oak, the cherry, pear, apple, ash, elm, and willow, are 

 examples of deciduous trees, their stems and branches 

 being leafless and naked during the winter season. Evei'- 

 greens are plants which continue to bear green leaves all 



