Davey . — Seedling Anatomy of certain Amentiferae . 599 
Summary. 
1. Members of the following cohorts have been examined : Verticillatae, 
Salicales, Mvricales, Juglandales, Fagales, and Urticales. 
2 . Diagonal types of transition are of frequent occurrence, and are 
correlated with the presence of large numbers of root poles and hypocotyl 
strands. 
3. Diarchy is characteristic of the Urticales and also of the Piperales 
described by Mr. T. G. Hill, but is otherwise seldom met with. 
4. The form of the vascular strands in the hypocotyl is remarkably 
constant, and is that of the triad defined by Dr. Thomas as the unit 
of hypocotyl vascular structure. 
5. The hypocotyl may contain triad units, in addition to those con- 
tinuous with the double bundles of the cotyledons, which are related in 
a similar manner to plumular leaf-traces. 
6. Doubleness of plumular leaf-traces occurs very generally. 
In conclusion, I wish to thank Dr. Thomas for much helpful criticism 
and advice, and also for having placed at my disposal for purposes of 
comparison her own preparations of the seedlings of other groups. 
