317 
lig. 17. The distal end of a hydrotheca from the abcauline surface. X 66. 
18. The distal end of a hydrotheca from the adcauline surface. X 66. 
19. The distal end of a hydrotheca showing the “A”-tent, formed 
by the two opercular membranes. 
— 20. The u A”-tent seen from above. X 66. 
— 21. Abietinella operculata (Jad.). X 34. 
— 22 a. The diaphragm of the same species. X 66. 
22 b. The opening of the diaphragm in Abietinaria Traski. X 66. 
28. A hydrotheca of Abietinaria coei Nutt. showing the stalk-mark 
and the adcauline internal tooth. X 34. 
24. A hydrotheca of Abiet. abietina L. showing the stalk-mark. 
X 20. 
25. Two hydrothecae of Abiet. variabilis after tlieir abcauline pro- 
jecting portion has been cut away. Distally is seen the boundarv 
line of the adcauline hydrothecal wall, and proximally the dia¬ 
phragm, the aperture of which is surrounded by a projectin£r 
margin, and the stalk-mark. X 20. 
26. A hydrotheca of Diphasia pinaster L, with stalk-mark. X 20. 
27. A hydrotheca of the same species after its abcauline projecting 
portion has been cut away. Proximally are seen the stalk- 
mark and the diaphragm. 
— 28—29. Sertularella magna Nutt. The distal end of a hydrotheca 
seen from the opposite sides. X 66. 
Plate V. 
Pig. 1. Hydrallmania plumulifera Allm. A portion of a proximal 
branch. Dorsal view. The hydrothecae, which show distinet 
stalk-marks, have been regenerated. X 34. 
2. The same species. A portion of a distal branch. Frontal view 
X 34. 
3. The same species. A portion of a distal branch. Lateral view. 
Distinet stalk-marks. X 34. 
4. The distal end of a hydrothecae, seen from the abcauline sur¬ 
face. X 66. 
5. The distal end of a hydrotheca, seen from the side. X 66. 
6. The distal end of a hydrotheca, seen from the adcauline surface. 
X 66. 
7. Hydrallmania falcata (L,). A portion of a branch. Lateral 
view. Distinet stalk-marks. X 34. 
8. Odontotheca operculata (L.). A portion of a branch. Frontal 
view. Distinet stalk-marks. X 34. 
9. The same species. The Distal end of a hydrotheca, seen from 
the abcauline surface. X 66. 
10. The distal end of a hydrotheca, seen from the adcauline surface 
and partly from above. The translucent abcauline sinus is 
seen. X 66. 
