24 The Neiv York State College of Forestry 



DENDROLOGY 



DENDROLOGY DEFINED 



The taxonomy of woody plants as distinguished from herba- 

 ceous is called Dendrology. Dendrology means literally the 

 "science of trees", but in general usage it has come to have a 

 broader meaning and to comprise a taxonomic study of all woody 

 plants. 



Unfortunately the line delimiting herbaceous and woody plants 

 is not a sharp one as the two types intergrade. Some plants are 

 always woody; others are herbaceous or semi-woody, but on occa- 

 sion may become woody. Tabulated below are the chief differ- 

 ences which distinguish woody plants, but it must be understood 

 in advance that the information thus imparted must be used 

 with reservation. 



CRITERIA1FOR5 DISTINGUISHING WOODY^[PLANTS 



1. Woody plants are perennial, that is, they live from year to 

 year. Annuals complete their life cycle within a season and 

 are tided over the winter by their seed. Biennials may produce 

 stems or canes, as in the raspberry, which are semi-woody the 

 second year, but the two-year life span precludes their inclusion 

 among typical woody plants. 



2. Woody plants possess vascular tissue, that is, specialized con- 

 ducting tissue. Not all vascular plants are woody by any means, 

 as all the herbaceous flowering plants are numbered among the 

 vascular plants. This prerequisite, however, excludes the Thal- 

 lophytes and Bryophytes from the category of woody plants. 



3. Woody plants possess an aerial axis or stem which persists 

 from year to year. In the case of a tree this stem is called the 

 bole or trunk. Many perennials fail to be classed as woody 

 plants because they die back to the ground each autumn, the roots 

 persisting through the winter and producing a new stem the fol- 

 lowing spring. Other plants, as many of the ferns, possess peren- 

 nial, creeping stems and are woody plants in a strict sense, but 

 not in the general sense as used in Dendrology. 



4. Woody plants possess vascular tissue which becomes 

 "lignified" or woody as it matures. This process of lignification 

 is brought about by certain chemical and physical processes which 

 take i)lace in the woody part of the vasenhu- tissue whereby its 



