7i 



Both J. G. Agardh (Till Alg. Syst. V. 1887, pp. 58 — 65) and De Toni (Sylloge Algarum 

 vol. I. 18S9, pp. 500 — 504) maintain the genera Penicillus and Rhipocepkalus as distinct, and 

 110 author would now question their validity. 



Finally, Monsieur Bornet (Algues de P. K. A. Schousboe, Paris 1892, in Mém. Soc. 

 nationale Sci. nat. et math. de Cherbourg T. XVIII. 1892 p. 57 (217)) includes Espera mcditer- 

 ranea Thur. in the £enus Penicillus. 



& v 



Morphological. 



Extern al characters. The thallus of Penicillus consists of root-mass, stipes and 

 capitulum. The plants grow either singly or together in clumps or in colonies. The local name 

 is "The Merman's Shaving Brush". In herbarium specimens the plant varies from green to 

 white, becoming bleached with age and exposure to light. Sometimes the stipes branches 

 dichotomously (as in P. dumetosus), and each branch bears a capitulum ; but in other species 

 the stipes is almost always unbranched. The root-mass is composed of long filaments bearing 

 lateral fascicles of long, straight, dichotomously branched rhizoids, which are generally matted 

 together into a compact mass with sand and calcareous débris. The stipes may be cylindrical, 

 or more or less compressed, and varies in length and width, being as a rule broad ancl com- 

 pressed in P. dumetosus (fig. 156) and narrow ancl cylindrical in P. capitatus (fig. 164). It 

 may taper downwards or rarely upwards. It is always calcified ancl varies from rigid to more 

 or less soft and compressible, being more or less hollow within as in P. Lamourouxii (fig. 162). 

 The surface has sometimes a velvety appearance, as in P. dumetosus and P. pyriformis, or 

 dull or polished as in other species. (For details of stipes-cortex see p. 75). 



The capitulum varies in shape and size. It may be large (10 — 15 cm.) composed of 

 long, wide, straggling, and but slightly calcified filaments, as in P. dumetosus-, or short (2 cm.) 

 globose and compact, composed of short, thin, rigid and well calcified filaments as in P. capi- 

 tatus. I he filaments of the capitulum may all arise close to the apex of the stipes or they 

 may emerge irregularly at some distance down the stipes as in P. capitatus f. elongatus 

 (fig. 1 66), giving the upper part of the stipes a whiskered appearance. The individual fila- 

 ments branch dichotomously, the points of dichotomy occurring at more or less regular inter- 

 vals, with the intervening portion of filament free from constrictions ; or the filaments may be 

 constricted in a moniliform or bead-like manner, as in P. 7iodulosus (figs. 173, 174). Further, 

 the successive dichotomies always lie in alternate planes, thereby distinguishing Penicillus 

 from Rhipocepkalus^ in which the dichotomies of the comal filaments lie in one plane. 



Structure. As regards the internal structure of Penicillus, we have very little to add 

 to the account given by Montagne in Dumont D'Urville's Voyage au Pole Sud (Botanique 

 vol. I 1845. pp. 26 — 29. pi. 14. fig. e — i). Montagne was in error in figuring and describing 

 the filaments of the capitulum of P. arbuscula (= P. nodulosus) as being septate (compare 

 our fig. 173(7); but apart from this we can confirm nearly all that he says. The few mam 

 filaments which constitute the skeleton of the stipes are modified into rootlets below and into 

 the free branches of the capitulum above. The main rootlets, 2 — 10 cm. long, fairly straight, 



