2(14 JOURNAL OF FORESTRY 



In the wood of Pinus alhicaulis the writer has observed the abnormal 

 development of wood parenchyma or resin cells described and figured 

 by Somerville (24). 



There is a close parallel between the conifers and dicolytedons in 

 the formation of intercellular passages. For discussions of the origin 

 and significance of such structures the reader is referred to the works 

 of Newcombe (22), Kirsch (35), and the numerous authorities cited 

 by the latter. Consideration of the phylogenetic significance of resin 

 ducts in conifers cannot be complete without taking into full account 

 the occurrence of similar structures in dicotyledons. Amplification of 

 this point is not within the province of this paper. 



Intercellular canals or ducts with contents of a resinous, gummy, 

 mucilaginous or other nature have been found in representatives (most- 

 ly tropical) of 23 families. 



As regards position in the tree these canals are of two separate and 

 distinct classes : vertical or axial, and horizontal or radial. As regards 

 origin they may be schizogenous, lysigenous, or schizo-lysigenous. The 

 ducts in the rays are mostly schizogenous ; the vertical ducts are in most 

 cases abnormal or pathological, often of the so-called gummosis type. 



The only families in which canals are commonly found in the med- 

 ullary rays are the Anacardiaceas, Araliacese. and Burseracese. Canals 

 are apparently of normal occurrence in certain representatives of seven 

 families, namely, Anacardiace^e, Araliaceje, Burseraces, Cornacese, 

 Dipterocarpaceae, Leguminosas (Csesalpinioideae), and Simarubacese. 

 Only in the Dipterocarpaceae are they the rule. 



The list of families of the dicotyledons in which intercellular canals, 

 either vertical (V) or radial (R) or both (very rarely together), have 

 been found in the secondary wood is given below. The arrangement 

 is alphabetical and the numbers indicate the natural order according 

 to the classification of Engler and Gilg (1912). The seven families 

 marked with an asterisk' (*) were not included in the former paper. 

 (Journ. For., 1G:4: 428-441.) 



LIST OF FAMILIES 



10. Anacardiacese (R and V) 12 *Malvaceae (V) 



19. Araliacese (R) 8. Meliacese (V) 



l.T. Bombacacese (V) 1. *Moringace3e (V) 



22. Borraginaceae (V) IS. Myrtaceae (V and R) 



