514 Howe: Phycological studies 



Hxplanatioii of plates 25-30 



Plate 25 



i-io. Halimeda Tuna 



I. Portion of a segment (decalcified), in radio-vertical section, showing peripheral 

 utricles, utricles of the subcortical layer, and medullary filaments. 



2 and 3. Peripheral utricles and utricles of the subcortical layer, decalcified and 

 teased out ; the peripheral utricles separating rather easily. 



4. Peripheral utricles, decalcified, in surface view ; no fusion is noticeable. 



5. Vertical section by microtome through the filament of the central strand (decal- 

 cified) at a node ; just above the points of fusion the filaments are somewhat enlarged 

 and are inclined to cohere. 



6. Two filaments from the central strand of a node, teased out, each formed by the 

 fusion of two; just above the points of fusion there has been considerable coherence of 

 the adjacent filaments and the outer layers of the filament-walls are more or less scarred 

 and lacerated by the process of teasing the filaments apart. 



7. A young simple sporangiophore. 



8. A sporangiophore from the margin of a segment, formed by the fusion of three 

 filaments of the central strand. 



9. A forked sporangiophore from the margin of a segment, formed by the fusion of 

 two filaments of the central strand. 



10. The beginning of a sporangiophore at margin of segment. (For sporangio- 

 phores of a different origin, see Plate 28, Figures i and 2. ) 



Figures l-io are all drawn from formalin-preserved material of our tio. 4201 

 (Culebra Island, Porto Rico) ; 1-6 are magnified 40 diameters; 7-10, 24 diameters, 



1 1-20. Halimeda discoidea 



II. Portion of a segment (decalcified), in radio-vertical section, showing peripheral 

 utricles of the subcortical layer, and medullary filaments. 



12 and 13. Peripheral utricles and distal ends of the utricles of the subcortical 

 layer, decalcified, showing contact of the peripheral utricles and their occasional inter- 

 locking. 



14 and 15. Peripheral utricles, etc., showing fusion as well as interlocking. 



16. Utricle of the subcortical layer bearing numerous peripheral utricles. 



17. Peripheral utricles, decalcified, in surface view, showing fusions; fusions of 

 two utricles are common ; near the upper left-hand corner and a little below the middle, 

 in the figure, are fusions of three utricles ; near the lower left-hand corner is a fusion of 

 four. 



18. Peripheral utricles, decalcified, in surface view, the dotted lines indicating the 

 form and position of the distal ends of the utricles of the subcortical layer, which are 

 often clearly visible through the peripheral utricles. 



19. Filaments from central strand of nodes, showing incomplete fusion. 



20. Filament from central strand of node, showing complete fusion of two fila- 

 ments to form one, which afterwards divides into three. The filaments shown in 

 Figures 19 and 20 are from the same node. 



Figures 11-20 are all drawn from formalin-preserved material of our no. 2g64 

 (Caesar's Creek, Florida) ; 1 1, 16-20 are magnified 40 diameters ; 12-15, 55 diameters. 



