LEA VES. 27 



appendages found in pairs at the base of the leaf-stalk : they 

 are generally absent in monocotyledons. 



Vernation, or the manner in which leaves are folded in 

 the bud before they expand, is a subject for the advanced 

 student. A thorough knowledge of leaves is of great 

 importance, since by it botanists are often able to classify 

 a plant when it is inconvenient or impossible to procure 

 other parts of it for examination. 



Venation means the distribution of veins in the leaves, 

 as mentioned in Lesson I. 



In the wattle and some other plants, the leaf- stalk is 

 sometimes so much flattened and extended as to resemble 

 a leaf. This peculiarity is termed a phyllode. In some 

 cases the true leaf is found growing at the end of the 

 phyllode. (See Plate III. figs. 3 and 4, p. 31.) In some 

 Australian wattles no true leaves are produced, the phyl- 

 lodes alone serving the same purpose. The leaf-stalks of 

 some water plants are filled with air, enabling the plant to 

 float or rise above the surface. 



Leaves are of two kinds, simple and compound. The 

 former vary in shape. They may be very deeply divided 

 towards the midrib; they may have one unbroken leaf; 

 yet they are simple leaves. The compound leaf has its blade 

 divided into leaflets, varying in number. The leaflets are 

 separated from the midrib by stalks. Beginners should be 

 careful not to fall into the error of calling leaflets leaves. 

 They are merely parts of leaves, as will be seen by the 

 following Diagram I. 



Leaves are furnished with stomata 1 or breathing apparatus, 

 often on both sides of the surface, but generally under- 



1 From stoma, a mouth. 



