I20 TEXTBOOK OF BOTANY 



foliage leaves of the pine are not borne directly on the trunk 

 or on long branches, except in the case of young seedlings. 

 The number of leaves in the cluster at the end of each spiu- 

 branch varies with the species ; for example, the red pine has 

 two needles in each cluster and the white pine has five. The 

 foliage leaves do not fall off at the end of their first season 

 as do the leaves of most of our common trees ; they Hve and 

 remain on the tree for more than one year. The leaves of 



Fig. 69. — Cross section through a foliage leaf of the Scotch pine ; a, epi- 

 dermis ; b, an air-pore ; c, layers of thick-walled cells just within the epi- 

 dermis; d, thin- walled cells between which are air-spaces; e, resin passage; 

 /, vascular bundles. 



some pines are said to live for ten years, but the average is 

 probably much less than this. A pine tree, at any rate, is 

 never bare of leaves, although each year some of the older 

 leaves drop off. When the leaves of a cluster fall, the spur 

 branch that bore them dies ; therefore spur branches and 

 foliage leaves (as well as scale leaves) are found as a rule 

 only on the younger portions of the trunk and of each long 

 shoot. 



A pine needle is not cylindrical, but has one or more flattened sur- 

 faces, depending upon whether it is one of a cluster of two, three, or 

 five which were pressed together in the bud. On both upper and 



