Tydemania, Pcnicillus, Rhipocephalus, and half of the genus Udotea (West Indian species with 

 one exception). 



Or (2) they occur a little way above the base of the branches and at unequal levels 

 (see fig. 47), as in Chlor odesmis comosa, Udotea javeusis, U. papillosa, U. glaucescens, U. 

 orientalis, U. indica, U. palmctta, U. argentea and Flabcllaria petiolata. 



The characteristic annular ingrowths and "stoppers" of Codiaceae have been so studied 

 and described as to require 110 special attention here. They occur in Codium, Chlorodesmis, 

 Rhipilia, RMpidodesmis, Callipsygma, Espera (i. e. Penicillus), and possibly in other genera. 



Calcification. All of the genera of the Udoteae are calcified. What is known of 

 the nature of the calcareous deposit has been summarised by Oltmanns (Morphologie und 

 Biologie der Algen II. 1905, p. 80). The researches of Meigen and others on calcareous algae 

 in general show that the calcium carbonate of the deposit may be in the form of aragonite 

 or of calcite, which two compounds can easily be distinguished from one another by means 

 of cobalt nitrate. The aragonite or calcite is never quite pure, but is mixed with magnesium 

 carbonate or with calcium oxalate in varying quantities, in different climates and in the different 

 eenera. There is need of further investieation in this direction. The calcareous matter is 

 deposited in the gelatinous layers of the outer wall, penetrating also into the cellulose inner 

 wall. Though the degree of calcification is to some extent a specific property, it also appears 

 to depend upon the degree of insolation to which a given plant is exposed ; for it may at 

 least be expected that it would be proportional to the amount of photosynthesis effected. 



As shown under Udotea (p. 102) and Pe?iicilhis (p. 72) there are two modes of calcification. 

 In the first, the filaments of the frond or capitulum are enclosed each in a porose calcareous 

 sheath (as shown in fig. 1S2). These filaments are either quite free as in the capitulum of 

 Penicillus, and the glomeruli of Tydemania expeditionis \ or they are laterally cemented side 

 by side into monostromatic flabella as in Udotea javeusis, U. glaucescens, Tydemania, Rhipo- 

 cephalus \ or they are more or less completely conglutinated together into a thicker (pluriseriate) 

 flabelliform or cyathiform frond as in U. conghitinata, U. eva thi 'form is, etc. 



The second mode of calcification is found in the cortex of the stipes of Udotea, Pcnicillus, 

 Rhipocephalus, and in the frond of the corticated species of Udotea. The apices of the simple 

 or branched lateral appendages of the main filaments of the stipes or frond are in this case 

 arranged so as to form a cortical covering to the stipes or frond, and are laterally coherent 

 into a continuous layer ; the laterally cohering walls are thickened by a calcareous deposit ; 

 and the actual apices are left free of calcification, and thus function as "windows" (see p. 103), 

 as in the cortical layer of the stipes of Penicillus (figs. 163, 168, 175) and Rhipocephalus 

 (figs. 186, 192), of the stipes and frond of Udotea faöellum and U. argentea, and of the 

 jointed thallus of Halimeda. How deeply this calcification penetrates into the thallus, and 

 whether it is limited to the cortical region, or more or less fills the inner cavities, we do not 

 know. But we should infer that it varies with the species and reaches for instance a deeper 

 level in the rigid stipes of Penicillus capitatus than in the softer stipes of P. Lamourouxii 

 var. gracilis. 



Pores and "windows". The pores, which are so abundant in the calcareous sheath 



