CHLOROPHYCE 161 
with no cross-walls, giving off rhizoids below and 
dichotomous branches above. Chamaedoris has a 
similar stalk, with its branches given off in a great 
terminal tuft—in habit like Peniczllus in this respect. 
It appears very probable ‘that the stalk is persistent 
and renews its crop of branches, both in this genus 
and at all events in some of the species of Struvea. 
The large species of Struvea are among the most 
beautiful of Alge. At the summit of the long 
rugose stalk without cross-walls there is borne a flat 
frond, through which the stalk is prolonged as a 
mid-rib. This mid-rib gives off opposite branches, 
which are again pinnately branched, and in some 
species these are similarly branched again and again. 
Where these pinne meet they are all bound by 
sucker-like haptera (Fig. 48¢), and the frond presents 
the appearance of a lovely piece of lace. 8S. plumosa, 
8. macrophylla, and 8. pulcherrima are the largest and 
finest species. Only three specimens of S. macro- 
phylla have been found, two of them being in the 
herbarium of Trinity College, Dublin, and one in the 
British Museum. 8. pulcherrima is even more rare, 
one specimen, not quite complete, being in the 
British Museum, and a fragment in the Edinburgh 
herbarium collected at the same time. The more 
slender forms have stalks unmarked by rugosities. 
The forms described as species of Spongocladia were 
long puzzling. They are dense wefts of interwoven 
filaments, with walls so much thickened in places as 
to obliterate the cell-lumen. They grow in intimate 
association (Symbiosis) with sponges, and assume to 
some extent the habit of these animals. It has 
M 
