Millerella myrioclada (Børgesen) G.H.Boo, 2016

Jamas, Mayra, Iha, Cintia, Oliveira, Mariana C., Guimarães, Silvia M. P. B. & Fujii, Mutue T., 2017, Morphological and molecular studies on Gelidiaceae and Gelidiellaceae (Gelidiales, Rhodophyta) from Brazil with description of the new species Gelidium calidum, Phytotaxa 314 (2), pp. 195-218 : 203

Millerella myrioclada (Børgesen) G.H.Boo

Figs. 3 C–D ; 4 K–N

Thalli erect, compressed, delicate and dark red, forming dense tufts, up to 1.5 cm ( Fig. 3 C ). Erect axes are sparingly and irregularly branched ( Fig. 3 D ). Apex acute with prominent apical cell having a pattern of malting division of subapical cells, resulting in an axial filament visible below the apex ( Fig. 4K ). Cross section of median region of the main thalli shows three layers of medullary cells formed by axial and periaxial cells produced in a distinctive transverse row of thick-walled cells that remain evident in most plant parts ( Fig. 4 L ). Rhizines absent. Fixing by independent rhizoidal filaments ( Fig. 4 M ). Tetrasporangia divided decussately cruciate, arranged in chevrons, thus V-formation without sterile margins ( Fig. 4 N ).

Figures

FIGURE 3. Habit of the Gelidiellaceae species. A. Gelidiella acerosa (SP469049). Scale bar = 1 cm. B. Gelidiella flabella (SP469052). Scale bar = 1 cm. C. Millerella myrioclada (SP469057). Scale bar = 1 cm. D. Millerella myrioclada (SP469057). Scale bar = 0.5 cm.

FIGURE 4. A–E. Gelidiella acerosa. A. Detail of the apical portion showing the prominent apical cell (arrow) (SP469045). Scale bar = 25 μm. B. Cross section of the middle region of the main branch (SP469045). Scale bar = 100 μm. C. Detail of main branch showing the transition from the cortex to the medulla (SP469045). Scale bar = 25 μm. D. Detail of the tetrasporangial branch with tetrasporangia (SP469046). Scale bar = 100 μm. E. Cross section of the tetrasporangial branch, showing tetrasporangia cruciately divided, with no sterile margin (SP469046). Scale bar = 100 μm. F–J. Gelidiella flabella (SP469052). F. Apical cell slightly different from the surrounding cells (arrow). Scale bar = 25 μm. G. Cross section of the middle region of the main branch. Scale bar = 250 μm. H. Detail of the cross section of the thallus showing the transition from cortex to medulla. Scale bar = 25 μm. I. Holdfast originated as independent rizoidal filaments.Scale bar = 100 μm. J. Cross section of the stoloniferous branch showing the origin of rhizoidal filaments from the outer cortical cell (arrow). Scale bar = 25 μm. K–N. Millerella myrioclada (SP469055). K. Detail of the acute apex with prominent apical cell. Scale bar = 25 μm. L. Cross section of the middle region of the main branch, showing row of medullary cells (arrow). Scale bar = 25 μm. M.Prostrate system. Scale bar = 250 μm. N. Tetrasporangial branch. Scale bar = 100 μm.