RESIN CANALS IN WHITE FIR 



353 



concentric layers of thick-walled trach- 

 eids of the late- wood (Fig. 3). Small 

 groups of resin cells may be distin- 

 guished from the large groups by the 

 fact that the latter are always sur- 



- tr-. 



rounded by 

 parenchyma 



during 



several rows of wood- 

 fibers containing starch 

 the winter. The structural 

 characters of the wood-parenchyma 

 fibers of the single resin cells are simi- 

 lar to those of the large groups, though 

 they are usually much longer, some- 



3t.C 



Z^j.S. 



times from .8 to i. mm. in length. 

 The individual starch cells of the wood- 

 parenchyma fibers are very much 

 shorter than the resin cells, varying in 

 length from .08 to .2 mm. 



3. True resin canals are present in 

 the wood of the roots, stems, and 

 branches. Dippel investigated sections 

 of wood cut from different parts of the 

 tree and determined that resin canals 

 are perpendicular structures extending 

 for a considerable distance, and that 

 they are not wholly independent of 

 each other, but communicate with one 

 another here and there. Dippel also 

 pointed out that resin cells originate as 

 such in the cambium, but for lack of 

 proper material he was unable to follow 

 in detail their subsequent development 

 to maturity. A very careful investiga- 

 tion of resin canals in young twigs, and 



also in mature wood cut from many 

 different parts of the stem, yielded im- 

 portant facts from which Dippel made 

 interesting deductions relative to the 

 origin and development of resin cells, 

 and which served him later in his study 

 of resin canals in Pinus, Larix, and 

 Picea. He found resin canals in all 

 samples of white fir and determined 

 that their presence cannot be regarded 

 in any way as abnormal. He also found 

 individual resin sacs similar to those 

 present in other coniferous woods, and 

 concluded that they are a result of ab- 

 normal cell development and a subse- 

 quent disorganization of their cell walls. 



