16 BRITISH MARINE ALG#. 
wall, which soon yields to the pressure from within, is finally ruptured, and 
through these minute orifices the zoospores make their way into the water. 
The ruptured filament on the right (Fig. 15) is empty ; three zoospores 
only are seen in the lower joint, five ciliated zoospores represent the 
active state of these bodies, and the two below represent the quiescent 
stage before germination. The ramification or mode of growth in the 
Cladophora, may be studied from an examination of the branch of Olado- 
phora Hutchinsie, p. 5 (Fig. 2). C. letevirens (d, Fig. 21) or the pale 
green Cladophora is one of the most common species of Cladophora met 
with on rocky shores. It grows in densely tufted masses very profusely 
branched, and beset on all sides with lesser branches and branchlets. The 
species in the illustration (Fig. 16) is C. diffusa, a loosely branched plant, 
rather rare, and the easiest to represent accurately in a drawing of any 
of these delicate alge. Terminal branchlets of two other rare species are 
represented in Figs. 17 and 18, C. rectangularis and C. falcata; the 
former being easily recognised owing to its branchlets and ramuli, all 
being set at right angles throughout the whole plant; the latter having 
branches shaped like sickles, the branchlets being curved in the same 
direction as their primaries and mostly on the inner or curved side. There 
are several other pretty species of this family, and among those which are 
parasitic on other alge may be mentioned the little cotton-like species 
known as C. lanosa, which grows near the forked tips of a dark-red plant 
called Polyides rotundus. I once found this tiny species in a beautiful 
Figs. 13, 14,15. Cladophora letevirens. 
Stages of development in the Fig. 16. Cladophora diffusa. 
endochrome. 
rock pool at Whitsand Bay, near Plymouth, growing on Polyides in such — 
profusion that the floor of the pool seemed as though it were carpeted 
with the most exquisite green velvet. Among the many species of Clado- 
phora which Iam tempted to describe, there is one which I may mention, 
though briefly, because it is met with very frequently about half-tide level, 
growing in rock pools and under the shade of the larger algw. Its name is 
