MODE ОЕ GROWTH ОЕ BALLIA CALLITRICHA AND В. SCOPARIA, 231 
DESCRIPTION OF THE PLATES. 
Puate XXVIII. 
Illustrations of the minute structure and mode of growth of Ballia callitricha. Figs 1-12 are from 
the fragments of this alga, gathered by Mr. Moseley, of H.M.S. ‘Challenger,’ in Kerguelen’s Land. 
Figs. 13-18 are from those obtained in the same island by the Rev. A. E. Eaton, during the Transit-of- 
Venus Expedition, and placed at the author’s disposal by Mr. W. T. Thiselton Dyer. 
Fig. 1. A portion of Mr. Moseley's plant : natural size. : 
Fig. 2. A portion of same, showing its habit and the fitful manner in which the ultimate branchlets are 
given off, and the paucity of any thing like the regular “ plumes ” of the other forms: x 20. 
Fig. З. A smaller portion, more highly magnified. The lower part of the figure shows the 6-sided 
ramification-cells, which therefore bear, besides the ordinary pinnz (branches), the accessory 
minor branchlets. Тһе upper part of the figure shows the 5-sided ramification-cells, which 
therefore are without the accessory branchlets. In some of the joints of the rachis the stoppers 
have become dislocated, and lie apart within the cavity. х 50. 
Fig. 4. A node or joint of a rachis, showing the dependent cortical investment and the bases, with the 
intervening “ ramification-cells," of four simple branches (i.e. without the accessory ones), the 
two lower being, of course, at the top of the next abutting joint beneath; the opposed pairs of 
stoppers can be seen above and below, the stopper at the top of the joint having become slightly 
displaced. x 100. | 
Fig. 5. Diagrammatic figure (founded, however, upon a young growing branch actually observed), showing 
the youngest and more advanced conditions of the ramification-cells. Тһе letter ? is placed 
against the septum in each case produced to cut off the triangular portion of the rachis-joint to 
become the ramification-cell. Тһе letters r c indicate in all cases the “ ramification-cell." 
The growing apical cell is still rounded ; when fully formed it becomes acuminate. 
Fig. 6. A branch given off from a cortical cell—that is to say, one of the component filaments of the great 
. plexus standing off from a main stem or principal rachis: greatly magnified. 
Fig. 7. Another filament giving off a branch in two places, also highly magnified : 7 с, ramification-cell. 
Figs. 8, 9. Side views of a node of a rachis under a still higher power. 
Fig. 10. Diagrammatic figure of the mode of growth of the ramification-cells, founded. on. cases actually 
observed in specimens: r c!, ramification-cell of the “ first” degree; r с’, of the “ second” 
degree. The figures 1-6 represent the different sides of the cell as adverted. to in the text ; 
aa, lateral pits and stoppers of the joint-cell ; 4, the terminal pits and stoppers. 
Fig. 11. Similar but more advanced, showing now the base of the accessory branch (hence necessarily 
the ramification-cell of the second degree) fully formed. The figures 17-8! represent the 
different sides of this cell, as adverted to in the text (the figures 1-6 and the letters а and 0 as 
in preceding). These two figures indicate the manner in which the projections from the base 
of each of the joints overlap and sit astride upon the apices-of the joints below, thus giving rise 
to the old error that they passed down into a pocket-like introversion of the same. 
Fig. 12. A stopper of large size, seen from its flat surface. 
Fig. 18. The Rev. A. E. Eaton’s plant, of natural size. 
Fig. 14. Same magnified, showing habit; near the top the branches simple, lower down showing 
