Different Types of Angiospermic Vessels. 185 
scalariform nature of such perforations is evident. Particularly intricate 
examples are found in some Compositae (Fig. 2) and Ericaceae, in Sauraja , 
Myrothalamus, Tetracera , Alsodeia, Cornus , and Tropaeolum (Fig. 5). They 
are of the same nature as the reticulate pitting which frequently accom¬ 
panies the scalariform pits of the side walls. It is well known that in the 
older vascular plants, at least, the multiseriate circular pits have been derived 
from scalariform pits through such reticulate conditions. 
Another kind of reticulate perforation is found in a few species. We 
may take as examples of these the vessels of Cordia illustrated in Fig. 3. 
Here the perforation is in the form of a rather regular uniform net. The 
individual openings in the net are approximately isodiametric and about the 
same size as, or slightly larger than, the bordered pits on the side walls of 
the same vessel. The whole net is about the same size as the simple per- 
Fig. 2. A, B. Reticulate perforations 
in Helianthus sp. 
Fig. 3. a, Reticulate perforation from Cordia 
inyxa. B and c, from Cordia saaveolens. 
foration of other types. In many cases the net sags down at the centre into 
the vessel-segment below it. This is shown in face-view, Fig. 3, B, and in 
section in Fig. 3, c. In these perforations there is no indication whatever of 
the scalariform condition or of the fusion of pits to form the individual open¬ 
ings. In fact these openings are little larger than the bordered pits of the 
side wall, and appear to have been formed by the loss of the membranes of 
the pits accompanied by a slight amount of enlargement. 
These reticulate perforations have been observed in several species 
of Cordia (Borraginaceae), Tecoma radicans (Fig. 4, a) (Bignoniaceae), 
Vitex alata (Verbenaceae), Bougainvillea speciosa (Fig. 4, b) (Nyctagina- 
ceae), and Boerhaavia sp. (Nyctaginaceae). They never occur to the exclu¬ 
sion of other types. In fact in every case observed the great majority 
of perforations are of the simple type, though examples of the reticulate 
type are present in most sections. Their occurrence is very sporadic. 
I have carefully examined many other species in the families to which the 
above-mentioned forms belong without finding any trace of them. They 
occur in forms where the great majority of perforations are simple. 
