60 
ing photograph (Fig. 10) the individuals are mostly two or three 
inches in height. Each of the radial chambers composing the 
wall of the cup is in large part a spore-case, containing in A, 
crenulatum from four hundred to five hundred round reproduc- 
spores produces internally a number of minute motile cells which 
are sexual in nature ig. 11 shows a row of ‘‘sea-bottles,” as 
they are often called — photographed from Porto Rican speci- 
mens now on exhibition in the museum. These grow especially 
r rk, usuall 
they are dark green and beautifully iridescent. The plant is 
Fic. 11. ‘*Sea-bottles”’ é Valonia ventricosa J. Ag.). From Porto Rico, 
(About one half natural size. ) 
simply a membranous sack filled with a semi-fluid protoplasm, . 
In the natural process of decay or when preserved in a fluid and 
exposed to the light they become as clear and translucent as a 
quartz crystal and are as attractive then as when living. 
In the exhibition cases adjacent to those containing the green 
algae we pass to the brown algae—the group which includes 
the largest kinds. The brown algae contain chlorophy], like the 
algae in general, but they have one or more brownish pigments 
in addition, so that the resulting shade is commonly a brownish 
green or a dark olive-green. The brown algae are nearly all 
found in salt water and comparatively few of them are small and 
