154 СЕКАМТАСЕАЕ 
Callithamnion Thouarsii Mont., described from Chile, is a 
much larger plant with distichously pinnate or even distichously 
bipinnate and more obtuse pinnae and there is no rhizoidal cell 
at the base of the pinna. We have been able to examine the 
original material of this species through the courtesy of Monsieur 
Hariot of the Muséum d’Histoire Naturelle of Paris. 
PLATE 30, FIGURES 8-17. Antithamnion densum 
= £ +1 £ 1 
8. Upper portion of one of with apical part of the main axis broken 
off. 
9. Apex of one of the main branches; a young sporangium at the left, below. 
то. Apex of pinna of typical form. 
тт. А portion of one of the main branches, showing pinnules, small basal cells рег- 
sisting after the fall of pinnae, etc. 
12, 13. Rhizoids from persistent basal cells of pinnae that have fallen and also from 
the basal cell of a pinna that persists. 
14. А mature sporangium, with one-celled pedicel; the same node bears also a sterile 
pinnule. 
15. À young sporangium, latero-terminal on basal cell of a 4-celled pinnule. The 
three distal cells finally fall off as the sporangium matures. 
16. А short fertile pinnule in which the sporangium springs from the second cell; 
the pinnule just above it is sterile, 
17. Two fertile pinnules, each of which conceals a second fertile pinnule behind it. 
gures are drawn from Coker 59 p.p. (Island of San Lorenzo). Figure | 
8 is enlarged 40 diameters; 11-13, 66 diameters; 9, 10, 14, and 17, 245 diameters; 
15 and 16, 390 diameters. 
PLATYTHAMNION J. Ag. Anal. Аш. 22. 1892 
PLATYTHAMNION ORBIGNIANUM (Mont.) J. Ag. loc. cit. 23 
Callithamnion Orbignianum Mont. Fl. Boliv. 7. pl. 7. f. 4. 1839: 
Kütz. Tab. Phyc. 11: pl. 84. f. II. 1861. 
Antithamnion Orbignianum De-Toni, Syll. Аш. 4: 1403. 1903. 
Attached to Gymnogongrus furcellatus growing on rocks near 
№. E. end of water front of Callao, Dec. 27, 1906, Coker 17 РР 
dredged in about five fathoms between San Lorenzo Island and | 
La Рипса, region of Callao, Feb. 5, 1907, Coker 58 f.p. id 
Montagne's original material of this handsome and well- _ 
marked species was also from the Callao region. His habit 
figure hardly does justice to the subdichotomous and forcipate- 
zigzag style of branching of the secondary and tertiary axes. His 
comparison of the form of the cauline cells to that of an hour-glass 
ша Варру one, but his artist was apparently in error (fig. 46) in 
showing a septum in the zone of constriction, The opposite 
