INTRODUCTION 31 



is a stand of characteristic form. The form of a stand 

 has reference to the arrangement among the different tree- 

 classes. The form depends primarily on the distribution 

 of the age-classes. Trees of different ages may mingle 

 together promiscuously; the age-classes may be in groups; 

 the trees may be all of about the same age; or there 

 may be a more or less complete canopy of crowns, and 

 underneath this a separate story of smaller trees, whose 

 crowns form a secondary canopy. The forms most com- 

 monly recognized are the following: 



A. High Forest Forms. 



1. Selection Form. Trees of different ages, from the 

 seedling to maturity, are represented, mingled individ- 

 ually or in small groups. 



2. Regular or Even- Aged Form. The trees are ap- 

 proximately even-aged. The term is not confined to 

 stands in which the trees are exactly even-aged. If the 

 majority of the trees have nearly the same age and their 

 crowns form a clearly defined, regular canopy, the stand 

 is classed as regular. In a virgin forest a stand is regular 

 if the majority of the trees are of merchantable size. 



3. Irregular Form. Through unregulated cuttings or 

 accidental injuries the stand has been broken and there is 

 an irregular representation of two or more ages. The 

 age-classes are not all at hand, and therefore it is not of 

 the selection form. The irregular form necessarily varies 

 enormously. 



4. Two-Storied Form. There are two distinct stands 



