CHLOROPHYCE 139 
of the cell. The chromatophores are rounded or 
polygonal, always with a clear central pyrenoid. 
Starch grains are very numerous, especially in the 
rhizoids, and are kidney-shaped in A. papuana and 
spindle-shaped in A. comosa. A yellowish or brownish 
colouring-matter is very abundant in the protoplasm 
and occurs very densely at the tips of the filaments, 
where it presents a dark resinous appearance. The 
rhizoids are less regularly dichotomous in their 
branching, and in most of the species enclose among 
the filaments masses of coral-sand, small shells, &c., 
so much so that the rhizoids of 4. papuana, when 
drawn forth from the mud or coral-sand in which the 
plant grows, present the appearance of a cylindrical 
mass of crumbling mortar. In A. longicaulis there 
are formed rhizome-like, creeping bodies that con- 
nect large numbers of fronds. They are round like 
the stalks, and of the thickness of a finger. In this 
way so many plants are connected—all of them 
ramifications of a single multinucleate cell—that 
probably there is no parallel to it to be found in the 
plant world in respect of its dimensions. 
Penicillus agrees in many essential respects of 
minute structure with Avrainvillea, such as the 
dichotomy of the filaments, but the plants do not 
outwardly resemble each other. The rhizoids are 
much alike, but the stalk is thickly incrusted with 
carbonate of lime, while from its summit the frond 
filaments wave free. Sometimes they are given off 
singly here and there from the surface of the stalk 
below the summit, but generally in a dense apical 
-mass like a mop. In some species the filaments are 
