Peer eer ee eee 
THE STRUCTURE OF THE WOOD IN THE PINEAE? 
IRVING W: BAILEY 
(WITH PLATE V)- 
The Abietineae have been conveniently divided into the subfami- 
lies Pineae and Abieteae.2 The former are characterized by the 
presence of resin canals in the xylem, by their thinly integumented 
ovules, and by the non-deciduous character of the cone scales. The 
Abieteae differ in having resin canals absent from the woody tissues 
of the stem (except in the first annual ring of vigorous shoots of vigor- 
ous specimens of Abies), and by possessing usually a thick-coated 
ovule and deciduous cone scales. In both subfamilies resin canals 
may occur traumatically. These are easily differentiated from those 
normal to the stem by the fact that they occur in tangential rows of 
numerous canals, intercommunicating tangentially, and composed 
of generally heavily pitted epithelial cells. The Pineae comprise 
_ the genera Pinus, Picea, Larix, and Pseudotsuga. The Abieteae 
include Abies, Tsuga, Cedrus, and Pseudolarix. It will be the object 
of the present article to consider the structure of the woody cylinder 
in the former subfamily. 
The four genera of the Pineae have been classified, by various 
authorities, according to the anatomical structure of the xylem as 
follows. 
PINUS 
The wood is characterized by the presence of numerous resin 
canals with thin-walled epithelium. This condition is constant except 
in the nut pines and foxtail pines of the southwestern United States, 
where thick-walled epithelial cells are interspersed among the usually 
thin-walled type. Further, Pinus is supposed to be characterized 
by the entire absence of wood-parenchyma, and according to GOTHAN 
of spiral thickenings of the tracheid walls of the secondary wood.* 
‘Contributions from the Phanerogamic Laboratories of Harvard University, 
No, 1 
Js FFREY, The comparative anatomy and ances of the Coniferales. Part 
2. The Abietineae. Mem. —_— oe Nat. ie t. s 21 5- 
3 GOTHAN, Zur Anat d fos Hélzer. Abhandl. 
K6nig. Preuss. Geol. Landesanstalt. eas Foie Heft ra p- 99. Berlin. 1905. 
47] [Botanical Gazette, vol. 48 
