72, 



In the West Indian species on the other hand, the stipes is developed early in the 

 young plant and grows to a considerable length (P. capitatus f. elongatus), perhaps to its full 

 size, and then the filaments, the formation of which has been postponed, develop at the summit 

 of the stipes. We have seen specimens which have a fully developed stipes hearing only a 

 few short, slightly calcified filaments at the .apex ; and Dr. M. A. Howe from personal obser- 

 vation confirms the fact of the stipes being formed before the capitulum in West Indian species. 



The stipes (or rhachis) evidently ceases from its growth when once the capitulum begins 

 to be formed ; and therein Penicillus differs from Rhipocephahts \ in which genus the rhachis 

 retains the power of slow continued apical growth for long after the first appearance of the 

 capitulum (see p. 92). 



R egener at io n. As regards the power of regeneration possessed by Penicillus, Miss 

 Elsie Kupper has shown (in Mem. Torrey Bot. Club. XII n° 3. 1907. pp. 227, 228) that plants 

 of P. capitatus, when decapitated, produced, after the lapse of about a month, a young head 

 of comal filaments. And the accompanying figure shows that similar filaments had broken out 

 singly or in groups along the stipes. 



Habitat. Penicillus grows on muddy sand and among débris of coral just below tide 

 limits. Mazé and Schramm (1. c. p. 91) record specimens of it as growing at Guadeloupe in 

 calm water on muddy sand at a depth of 1 meter, and again on reefs in the open or among 

 banks of Zostera at a short distance from the shore. Dr. Howe found P. capitatus in 3 — 10 dm. 

 of water at Key West and P. dumctosus in mangrove mud near low water mark in Florida. 

 Mrs. Pease whose name is well-known as a collector in the West Indies writes: "Penicillus 

 " dumetosus grew in some abundance in a pool near Manchioneal. The pool was narrow, with 

 "precipitous tufa walls, which towards the sea closed over the pool in an arch through which 

 "the waves broke heavily. The Penicillus grew among eelgrass, in muddy soil covered by a 

 " coating of powdered shell and coral. With it were P. capitatus, Avrainvillea longicaulis and 

 " Halimedas. The P. dumctosus lookecl like miniature groves of carefully trimmed evergreen 

 "trees, grey green in colour". Mrs. Pease in Collins' Algae of Jamaica. Proc. Amer. Acad. 

 XXXVII. Nov. 1901. p. 245. 



The colour of living plants varies according to the amount of calcification from a full 

 deep-green to grey-green. 



F r u c t i f i ca t i o n. No information of a satisfactory character has ever been published 

 about the reproduction of Penicillus. The bodies which Woronine observed in P. mediterra- 

 neus and which with much doubt he suggested might be zoosporangia, need re-in vestigation. 

 The problem of the propagation of Penicillus is one which can only be solved by a careful 

 stucly of the living plants. 



Duchassaing (Animaux Radiaires des Antilles. Paris 1850, pp. 27, 28) has stated that 

 Nesea [= Penicillus] is propagated by sporules and by propagules. As regards the former he 

 erroneously assumes that the numerous pores in the incrustation, which are sometimes open, 

 sometimes closed, are oviferous capsules. As to the propagules, he describes and figures the 

 development in Nesea pcuicellus [= P. capitatus], saying that a surculus, given off by the 

 tufted roots, travels under the sand for a distance of 10 — 12 inches from the mother-plant, 



SIISOGA-EXPEDITIK I.X1I. IO 



