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THE ROYAL SOCIETY OF CANADA 



examined, only a few pits were discovered. These proved to be, in all 

 instances, of the same type as the "vestigial centripetal xylem" of the 

 ordinary form. The longitudinal walls of the elements composing 

 this tissue are, moreover, very thin and the slightly tapered or hori- 

 zontal end walls often show pit-like thickenings. There is a sharp 



Fig. 11. — Pinus strohus. 

 Adult Polyphyllous — long. tang, above protoxylem — x 200. 

 e. — Endodermis; tt. — transfusion tissue; 

 tt.p. — Pitting on* tt; v.cp. — Vestigial 

 centripetal xylem; v.p.cp. — Pitting on 

 v.cp. 



distinction between the elements of transfusion tissue and those of this 

 vestigial centripetal xylem (Fig. 11). This condition we have seen 

 pertains as well to the adult, which differs only in the smaller 

 development of the tissue in question. 



Unfortunately, all polyphyllous material had been preserved for 

 an indefinite period in strong formaldehyde solution, which had so 

 greatly distorted the tissues it was found necessary to treat the 

 material with "eau de javelle." This subsequently interfered with 

 the ready absorption of staining reagents and consequently increased 

 the difficulty of interpretation. For instance, it cannot be concluded 

 that the vestigial pitting found represents the maximum of develop- 

 ment for the form, nor yet can it be compared with any certainty in 

 this respect with that of the ordinary type. 



The Primordial Leaf. The primordial leaf, which occurs normally 

 on the seedling, in advance of the fascicled condition, and occasionally 

 on the adult, as a traumatic response, is conceded by morphologists to 

 be more primitive than the adult leaf. 



Fig. 12 is from a transverse section at about the centre of a 

 primordial needle. The pericycle consists of numerous tracheary 



