Intenwdal Vascular Strands of Equisetum. 25 
initiate branches relatively early in the phylogeny; and correlated 
with this loss certain species have ceased, or are ceasing, to produce 
lateral metaxylem in this region. 
Perhaps, even to-day, it is not useless to add that in expressing 
the conviction that the internodal strands of Equisetum are 
phylogenetic units that may conveniently be termed bundles, it is 
by no means intended to suggest that these strands are in any 
strict, scientific sense equivalent to the ordinary internodal bundles 
of the Angiosperms. The fact that such bundles are common, 
whereas, in Equisetum , the bundles contain some purely cauline 
vascular elements, constitutes a real difference between the two 
types. Moreover, it seems particularly gratuitous to seek for strict 
stelar homologies between groups so remote from one another and 
of such very different antiquity as the Equisetales and the 
Angiosperms. 
LITERATURE QUOTED. 
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4. Buchtien, O. “ Entwicklungsgeschichte des Prothalliums von Equisetum .” 
Bibliotheca Botanica, No. 8, 1887. 
5. Campbell, D. H. “ Mosses and Ferns.” Second edition, 1905. 
6. Duval-Jouve, J. “ Historic naturelle des Equisetum de France,” Paris, 
1864. 
7. Eames, A. J. “ On the Occurrence of Centripetal Xylem in Equisetum." 
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9. Gwynne-Vaughan, D. T. “ Remarks upon the Nature of the Stele of 
Equisetum .” Annals of Botany, 1901. 
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11. Leclerc du Sablon. “ Sur les tubercules des Equisetacees.” Revue 
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12. Milde, J. C. “ Monographia Equisetorum.” Nova Acta Academise 
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