CHLOROPHYCEJE 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 A. 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 



