106 ^lyJESSOJyS WITB PLANTS 



together with certain morphological considerations, 

 cause it to be regarded as a leaf -like petiole. 



115a. This particular type of leaf — one which is interpreted to 

 be a modified petiole — is called a phyllodium. 



116. Another acacia is shown in Fig. 

 104. Here the phyllodia are present, 

 standing edgewise. But there are also 

 spines beneath them. If the criterion 

 of mere position is to be followed, we 

 should consider these phyllodia to be clad- 

 ophylla ; but the leaves of young seed- 

 lings and evidences of morphology show 

 that the spines are probably stipules of 

 the phyllodia. If, now, we return to the 

 phyllodia in Fig. 103, we notice a minute 

 scar at the base of each (indicated by 

 the spot at the. base in the picture). This 

 mark is not uncommon in these acacias, 

 and it suggests a remnant, perhaps, of 

 stipules. It is seen, therefore, how great 

 Fig. 105. the importance of very obscure characters 

 Leares of may be when one studies the changes, or 

 ' the evolution, which plants have undergone. 

 117. Leaves of the common white pine of the 

 North are shown in Fig. 105. It is seen that 

 there are five of them together. (The pupU 

 should examine the different kinds of pines, and 



