PHAZOPHYCEA 101 
tion of the long branches the activity of the growing 
point is mainly directed to the development of the 
branches below the growing point, while during 
the formation of the short ones, most of the cells 
produced reinforce the growth in length of the 
terminal shoot. 
The Reproductwe Organs.—Unilocular sporangia 
are known in WDesmarestia viridis, and are the 
equivalents of superficial cells. In <Arthrocladia 
club-shaped chains of cells arising above the growing- 
point of the short branches form the plurilocular 
sporangia. Farther information is greatly needed on 
the subject of the reproductive organs of this group, 
and observations on the species of Desmarestia in 
particular. 
The Geographical Distribution is mainly in the 
north and south temperate seas. Arthrocladia villosa, 
and Desmarestia viridis, D. aculeata, D. ligulata, D. 
Dudresnayt are British, but most species of the 
latter genus belong to the southern ocean. 
STRIARIACE. 
General Characters—The thallus, which attains 
considerable length in many of the forms, is of 
parenchymatous structure, and variously branched. 
It grows in length at a meristematic region below 
the apex. Both unilocular and plurilocular spor- 
angia occur, developed as equivalents of superficial 
cells or as outgrowths of such. 
The Thallus, which is rarely simple, but in most 
