/ 



334 Howe: Acicularia and Acetabulum 



19. Terminal portions of young sporangia from the preceding, X 4°- 



20. Prolification of axis, X l6 - At about the lower third are scars left by the fall 

 of a whorl of primary sterile branches ; above this an apparently abortive disc-rudi- 

 ment ; at the apex, the beginnings of another whorl of primary sterile branches. 



21. Prolification after the fall of a disc, X I0 - 



22. Prolification and dichotomy, X IO - 



Plate 25. Acicularia Schenckii (Mob.) Solms. 



23. Plants with mature discs, natural size. 



24. A mature disc viewed from above, X 7- 



25. Apex of mature sporangium, surface view, showing the small terminal 



apiculum, X 4°- 



26. Another sporangium-apex in optical section after decalcification, X 4°- 



27. Coronal processes, X5S* 



28. Coronal process, with two scars left by the fall of disc-filaments, X 2 45- 



29. Coronal process with transverse invagination, one disc -filament -scar, and one 

 abortive rudiment of a disc-filament, X 2 45- 



30. Coronal process with transverse invagination, after decalcifying, X 2 4S- 



31. Hypopeltal processes, X 55- 



32. A single hypopeltal process, with vestibule below, X 2 45- 



33 and 34. Slightly diagrammatic radial sections, showing relations of the various 

 parts of the disc, X *8o. a, the disc-filaments or their rudiments ; b, the sporangium ; 

 c, the hypopeltal process ; the dotted line marks the inner lateral boundary of the vesti- 

 bule. In Fig. 33 the coronal process shows a transverse invagination. 



35. Vestibules viewed from the main axial cavity of the plant, X 2 45-* ^ n eacn > 

 the passage-way leading into the coronal chamber is seen to be elongated transversely 

 to the plant axis ; the appearance of this passage-way in vertical section is shown in 

 Figs. 33 and 34. 



36. A single mature sporangium viewed from above, showing toward the apex the 

 falling away of the sporangium wall and the resultant exposure of the aplanospores, 

 X 16. Drawn from a glycerine mount. The aplanospores are as a rule less clearly 

 visible through the sporangium wall, even in a glycerine mount, than the present figure 

 would indicate. 



37. A spore-mass (massula) removed from the sporangium entire, viewed from 

 above or below (using these terms with reference to its former position in the disc), 

 X16. 



38. The same massula in lateral view, X 16. 



39. Portion of massula in surface view, X 55- 



40. A single aplanospore with its calcareous incrustation, in optical section, 



XI93. 



41. Aplanospore with calcareous coating fallen away, X *93* 



42. Aplanospore, showing operculum, after treatment with strong acetic acid, 



X245- 



43. The operculum and adjacent portions of the aplanospore wall, in optical sec- 

 tion, after treatment with strong acetic acid, X 75o (reduced from 1500). 



Columbia University, May 16, 1901. 



