128 CONIFBEALES (RBCBNT) [CH. 



America, Mexico, and Florida. Torreya has a more restricted and 

 less continuous range in China, Japan, Florida, and Cahfornia. 

 Torreya taxifolia is almost extinct ; it is separated by over 3000 

 miles from the other American species T. calif ornica and the Pacific 

 separates the latter from the two species in China and Japan^. 

 Cephalotaxus hves in central China, Japan, and India. 



Anatomical features. 



The anatomy of Conifers, more especially from the point of 

 view of the identification of families and genera, has long occupied 

 the attention of botanists, and although much has been done in 

 the direction of more intensive study, the Umits within which 

 anatomical features may be safely used are still but vaguely 

 defined. Jeffrey^ goes so far as to claim for the anatomical 

 characters of plants a taxonomic value equal to that assigned by 

 zoologists to the anatomical features of animals. Though often 

 extremely useful, ia many cases anatomical characters do not 

 reveal more than an affinity between a fossil specimen and a group 

 of recent genera. Statements are often based on insufficient data 

 and many authors have not appreciated the range of variation 

 in the vegetative shoots of a single tree. Attention has been 

 drawn to the fact that anatomical features are especially variable 

 in branches, and several authors have shown that characters to 

 which importance has been attached are much less constant than 

 has usually been supposed : many features, frequently accepted 

 as trustworthy criteria from the point of view of identification, 

 occur sporadically in other genera than those with which they are 

 usually associated. In the following summary attention is directed 

 to the comparative value of different characters, and prominence is 

 given to possible sources of error in inferences based on anatomical 

 features. 



The wood of a Conifer consists only of tracheids, with or without 

 resin-canals, and xylem-parenchyma and is characterised by 

 narrow medullaiy rays usually one-cell broad. For convenience 

 in description it is proposed to speak of the wood of the Conifer 

 type as pycnoxylic^ in distinction to the Cycadean type of 

 wood which is styled manoxylic. The presence or absence of 



1 Berry (08^) p. 648. 2 Jeffrey (05) p. I. 



^ TTvKvds. compact ; /uai/os, porous, loose in texture. 



