156 THE BIOLOGY OF FLOWERING PLANTS 



flower. In open stations they are soon lost and the narrow 

 adult type is produced. In the trees the sun leaf is a typical 

 adult leaf, and the shade leaf a typical youth form. The 

 correspondence may be seen from some of Nordhausen's 

 measurements given in Tables XXX and XXXI. 



TABLE XXX 

 Structural Characters of Sun and Shade Leaves of the Beech 



TABLE XXXI 



Comparison of Apical and Basal Leaves of Beech Shoots 



In Table XXX we have exhibited the characteristic differ- 

 ence between extreme sun and shade leaves in the grown 

 tree. In the seedling there is much less difference between 

 the two ; the characters of the shade leaf are even more 

 pronounced, while the sun leaf comes very near the shade 

 leaf of the adult tree. As Table XXXI shows, on a single 

 shoot of the adult tree the basal leaves are always relatively 

 of the shade leaf type, though it is only in well-shaded 

 basal leaves that the character of the seedling shade leaf is 

 approached. 



These results show that the production of the sun or 

 shade type of leaf under appropriate conditions is less a 

 direct structural modification than the resumption or 



