VESSELS OF THE GNETALEAN TYPE IN ANGIOSPERMS' 
EC. MACD UFETE 
(WITH PLATES XXIX—XXXII) 
A common feature of Gnetales and Angiosperms is the possession 
of true vessels. The evolution of the vessel perforation and its 
typical form have long been matters of investigation. ‘THOMPSON’ 
has stated recently that the derivation and evolution of the vessel 
in Gnetales is distinct and different from that found in Angiosperms. 
On the other hand, SOLEREDER? and DEBAry‘ mention the existence 
among certain Angiosperms of the peculiar bordered pore which — 
THompson so definitely limits to the Gnetales. The present investi- 
gation, which covers a number of species of Angiosperms and 
Gnetales, confirms and extends the observations of SOLEREDER and 
DeBary on Angiosperms and of THompson on Gnetales. The 
writer finds it necessary, however, to differ from the conclusions 
of THompPsoN on Angiosperms. 
Gnetales 
In Ephedra, the lowest genus of Gnetales, primitive conditions 
of vessel organization are found. Fig. 1 is a section of wood taken 
in a primitive region near the pith. To the extreme left are the 
long slender tracheids with their characteristic pits, bordered and 
containing a torus. In the center are two large vessels which, in 
their several ways, show a distinct relation to and evolution from 
the tracheid condition. The vessel more to the left has pits of 
ordinary tracheary type at either end, except that they are some- 
what enlarged in the vessel condition, but retain both border and 
Contribution from the a of Plant Morphology of Harvard University. 
2 THompson, W. P., Indep tion of ls in Gnetales and Angiosperms. 
Bor. Gaz. 65 :83-90. 191 18. 
, Anatomy and relationships of the Gnetales. 1. Ephedra. Ann. Botany 
sbi toreivac Ig12. 
3 SOLEREDER, Hans, Systematische Anatomie der Dicotyledonen, Stuttgart. 1899. 
* DeBary, H. A., Comparative anatomy of the vegetative organs of the Phan- 
erogams and Ferns. Trans. by F.O. Bowerand D.H.Scorr. Oxford. 1884. 
Botanical Gazette, vol. 71] 
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