75 



teristic, and, when once learned, affords a ready means of distinction ; it is however extremely 

 difficult to define in words, though easily expressed in drawings. A strong systematic character 

 is afforded by the calcified cortex of the stipes in some of the species, when examined under 

 a low power (X 30 — 40) of the microscope. In two of the species, P. dumetosus (fig. 159^) 

 and P. pyriformis (fig. \~j\a), the stipes-cortex is seen to be caespitoso-papillose, vvhile in all 

 the rest the cortex appears pseudoporose, that is, porous, but with the pores closed by a 

 thin film. The pores are comparatively large in P. Lamourouxii and its var. gracilis (fig. 163c?) 

 and P. nodulosus (fig. 1 7 5 <rr), and very small in P. capitatus (fig. i68<?) and P. mediterraneus 

 (fig. i8o«). They are still more minute in Rhipocephalus phoenix (fig. iSótf). These papillae 

 and pores represent the ultimate divisions or apices of the lateral appendages of the main 

 filaments of the stipes, as may be seen after decalcification and dissection. 



The absence or presence of bead-like constrictions in the filaments of the head is only 

 useful as a systematic character in dividing P. nodulosus, the Australian species, from all the 

 others. In P. nodulosus the filaments are constricted in moniliform rows of varied length, 

 while in the rest of the genus such beading occurs but irregularly and much less markedly, 

 and forms no distinctive character. 



Up to the present time the fructification of Penicillus has not been seen. It is possible 

 that this, should it exist, might add a systematic character to the definition of the species. 



Penicillus Lamarck 

 Sur les Polypiers empatés, in Ann. Mus. Hist. Nat. Paris XX. 18 13. p. 297. 



Nesaea Lamouroux Mém. class. Polyp. corall. in Nouv. Buil. Sci. Soc. Philom. Paris III. 



i8r2. p. 185. 

 Nesea Lamouroux Hist. des Polyp. corall. flex. 18 16. p. 253. 

 Coralliodendron Kützing Über d. Polypiers calcifères des Lamouroux in Oftent. Prüf. Realschule 



Nordhausen 1841. p. 11. 

 Penicillus Decaisne in Ann. Sci. Nat. 2<= sér. torn. XVIII. 1842. p. 96. 

 Corallocephalus Kutzing in Linnaea XVII. 1843. p. 95; Phycolog. generalis 1843. p. 310. 

 Poropsis Kützing Tab. Phyc. VI. 1856. p. 29, tab. 85, I. 

 Espera J. G. Agardh Till Alg. Syst. V. 1887. p. 55. 

 Penicillus J. G. Agardh op. cit. p. 58. 

 Espera De Toni Syll. Alg. I. 1889. p. 499. 

 Penicillus De Toni op. cit. p. 500. 



Penicillus Collins Green Alg. N. Amer. in Tufts College Studies II. 1909. p. 391. 

 Penicillus Wille in Engler und Prantl naturl. Pflanzenfam. I. Teil, 2. Abteil. 1890. p. 141, fig. 93. 



Thallus composed of stipes, capitulum and root-mass. Root-mass fibrous, long, branched, 

 sometimes matted into a dense bulb. Stipes erect, usually terete, encrusted externally, hollow 

 and laxly fibrous within (when dry), composed of numerous unicellular, longitudinal, interwoven 

 filaments, dichotomously branched and bearing lateral appendages, the peripheral endings of 

 which are approximated together to form a cortex, which becomes thickly calcified. Capitulum 

 composed of a more or less dense, brush-like tuft of unicellular free filaments; filaments repeatedly 

 dichotomous in alternating planes, sometimes trichotomous, constricted at base of each branch 

 and elsewhere ; branches always spreading, covered with a porous calcareous pellicle. 



