ANATOMY AND PHYLOGENY OF THE CONIFERALES. 



21 



noted that certain genera, of the Abietineae were characterized by the abtindanl occur- 

 rence of resin canals in the secondary wood of their vegetative and reproductive axes and 

 in the secondary wood of the root as well. In these genera resin canals are also abun- 

 dant in the cortical tissues of all the organs. They are further characterized by their per- 

 sistent cone scales. 



In contrast to these are a number of genera in which the resin canals, so abundant in 

 the forms just described, are almost entirely absent in the secondary woody tissues of the 

 vegetative and reproductive axes. Where they do occur in the secondary wood of the 

 stein organs, they are confined to the female reproductive axis, and to the first annual ring 

 of vigorous branches of sexually mature trees. These genera are further particularized 

 by the fact that in the woody tissues of the root, resin canals are confined to the primary 

 wood, but are never absent from this position. In the cortical tissues of some of the 

 genera included in this group, resin canals are abundantly present, but in others they 

 occur only in the female reproductive axis and its appendages, and in the mesophyll of the 

 leaves. Although resin ducts are normally absent in the secondary wood of the vege- 

 tative axial organs of the genera under discussion, their formation may be brought about 

 in dense tangential rows by the attacks of fungi, or by mechanical injury. Finally the 

 genera included here are with one exception characterized by deciduous cone scales. 



The genera to be included in the first group are Pinus, Pseudotsuga, Larix, and 

 Picea. The second group contains the genera Abies, Pseudolarix, Cedrus, and Tsuga. 

 It seems advisable to include the first four genera in a special subfamily, the Pineae, and 

 the last four in another special subfamily, the Abieteae. These two series are so distinct 

 in both their reproductive and anatomical characters, that it will conduce to a clear under- 

 standing of their phylogenetic relationships to keep them separate under the designations 

 which have been suggested above. 



Having separated the genera of the Abietineae into two distinct groups we may now 

 go on to inquire how these two groups are related to each other and which of them is the 

 more primitive. Further, after having as far as possible from the data here made avail- 

 able, settled their general relationship, we may advantageously pass on to the consider- 

 ation of the affinities of the several genera which they include. 



As a preliminary to the discussion of the relative antiquity of the Pineae and 

 Abieteae as here defined, it will be convenient to recall the anatomical differences 

 between the two subfamilies. The Pineae are characterized by the presence of resin 

 ducts in the woody and cortical tissues of their stems and roots. There are peripheral 

 resin ducts in the primary wood of the root and similar ducts are in some cases found in 

 the primary wood of the stem. The integument of the ovule is relatively thin and the 

 scales of the cone are not deciduous. In the Abieteae on the other hand, resin canals are 



