560 PROCEEDINGS OF THE AMERICAN ACADEMY. 



stant feature and shows various stages of degeneracy the canal often 

 for instance being largely or even wholly blocked with tyloses. 



The occurrence of resin-canals in the scale bundles in a species of 

 x\gathis is a feature of considerable interest phylogenetically. The 

 question at once arises whether it is to be regarded as an inchoative 

 stage in the development of resin canals in the group or a vestigial one. 

 Its place of origin appears to negative the former hypothesis. We 

 may in fact compare the occurrence of vestigial resin-canals in the 

 xylem strands of the peduncle of the cone in Agathis Bidwillii, with 

 the development of vestigial centripetal wood in the peduncular region 

 of the cone of certain Cycads, the very interesting and important dis- 

 covery of Dr. Scott *° or the existence of the same ancestral type of 

 xylem development in the strobilar organs of Equisetum, long after 

 it has disappeared in the vegetative axis of the ancient stock from 

 which that genus has been derived. ^^ The resin-canals in question are 

 also to be regarded as ancestral on account of the wound reactions of 

 Mesozoic xA.raucarian woods, which have been discussed above. These 

 interesting vestigial resin-canals appear in the vascular supply of the 

 lowermost abortive cone-scales, attached to the peduncle of the cone, 

 and die out before the cone-scale supply leaves the wood of the pedun- 

 cular axis. They have as yet been found only in Agathis Bidwillii. 

 It does not appear at all likely that they will be discovered in other 

 living species of the genus Agathis. It is probable on other grounds, 

 that this species is the most primitive now in existence. 



It naturally has occurred to the writer to investigate the wound 

 reactions of the stem and roots of living species of Agathis and Arau- 

 caria. The results of extensive examinations of wounded material 

 from the iVustralasian and East Indian regions ha\'e however been 

 entirely negative. There is reason to suppose however from a series 

 of investigations carried on with another purpose that traumatic 

 reactions in the seedlings, particularly the seedlings of Agathis Bid- 

 willii, may yield more favorable results, since it has been found in 

 certain instances that seedlings respond much more readily to experi- 

 ment than does the adult plant. It seems clear that so far as the 

 mature individuals are concerned, howe\'er, that the living representa- 

 tives of the Araucarian stock have entirely lost their capacity for 

 producing reversionary wound resin canals, and in this respect as in 

 other equally important normal features of stru'^ture, differ from a 



40 Scott, D. H., The Anatomical Characters of the Peduncles of Cycada- 

 ceae, Ann. Bot. II (1897). 



41 Eamcs, Centripetal Xylem in Equisetum, Ann. Bot. 23, (1909). 



