158 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



branches terminated by a large apical cell which by transverse, longitudinal, 

 and oblique division produces a plant body, the external surface of which is 

 composed of rectangular cells arranged in regular, transverse bands. Uni- 

 locular and plurilocular sporangia mostly extra-axillary on the branches, on 

 a one- to few-celled stalk ; propagula known in most species, on separate 

 plants. 



28. Sphacelaria tribuloides Menegh. 



Plate XXVI. 



Sphacelaria tribuloides Menegh., Lett, al Corinaldi 2, N. i; Aig. Ital., 

 336, 1842. 



Plant densely tufted, olive-brown ; primary branches somewhat dichot- 

 omous, appressed, bearing above numerous alternate or opposite branches. 

 Main filament composed of 4-S siphons, 50-70/^1 wide, the external cells \-yi 

 as long as the diameter of the filament ; propagula obcordate on the upper 

 branches ; plurilocular sporangia elliptical or obovate, 75-r5o/>t x 50-70//, on a 

 one- to four-celled stalk. 



The plant forms dense tufts 1-3 or 4 cm. high, on rocks -at 

 the low tide Hne. Collected by Prof. A. J. McClatchie. 



Sphacelaria didichotoma, sp. nov. 



Plate XXVII. 



Plant forming small, cushion-like masses 2-4 mm. high. Erect filaments 

 arising from a small compact substratum, bearing many long, spreading, 

 alternate branches ; main filament 25-35// broad ; external cells Yz to as long 

 as the diameter of the filament ; axis of the filament of four or five siphons ; 

 propagula abundant, large, twice dichotomus, often standing at right angles 

 to the main filament ; stalk 2-300// long, main branches 100-200//. long. 



Forming small, compact tufts on Melobesia and Ahn- 

 feldtia. Carmelo Bay, California. 



Family ENCCELIACEvE (Kuetz.) Kjelhn. 



Encosliacece (Kuetz.) Kjellm., Phyc. Gener., 336, 1843. 



Reproductive organs developed from superficial cells or from one of the 

 divisions of a superficial cell ; plant tissue of parenchymatous structure ; 

 growth intercalary, growing point near the base. 



