PIPER ACE JE. 485 



and frutescent species the wood is compact, in layers, traversed by 

 large medullary rays." We find numerous variations in detail in the 

 different species. Unger 1 demonstrated in 1S40 that some Piperads 

 have two fibrovascular systems, a central and a peripheral. In the 

 internodes their course is parallel, without anastomosis, but at the 

 nodes they unite to form a plexus, whence the buds and roots take 

 origin. Wood-formation is limited to the outer system, on the 

 external surface of which are produced new bundles, composed of 

 vessels and connective parenchyma. 3 Hence the stems only become 

 hard and woody in those plants which possess an external fibro- 

 vascular system ; they are herbaceous where there is only the primi- 

 tive system with scattered bundles ; thus it is that C. De Candolle 3 

 distinguishes Peperomiece (herbaceous) from Piperece proper (woody). 

 The perfect decussation of the leaves in Chloranthem leads to a regular 

 arrangement of the bundles. In Chloranthus inconspicuus there were 

 found 4 four large bundles arranged in a square, in each internode. 

 " These four large bundles are separated, each from its neighbours, 

 by a pair of smaller ones which join together. When the bundles 

 are fully developed they have all the general characters of the 

 Dicotyledonous stem. The anatomical structure of Ceratophyllea? is 

 quite peculiar, and correlated with their aquatic habitat. In the 

 arrangement of its parts the stem recalls that of plants widely 

 separated in other respects, but of submerged habit. Beneath the 

 epiderm is a copious thick cortical parenchyma, with its cells full of 

 pink liquid, or starch and chlorophyll. But its deeper layers are 

 traversed by enormous tubular spaces filled with gas, separated from 

 one another by vertical septa often consisting of a single stratum of 



1 TJeb. d. Bau uad das Waehsth. d. DicoL 9, 10. — Lindl., Veg. Kingd., 515. — Henfe., 

 Stam. Petersb. (1840). — MiQ., Comm. Phyt. Flem., 533. — Oliv., Stem in Dlcot., 32 (in Nat. 

 (1838-40), 3; Syst. Piperac, 5, 7; in Mart. Hist. Rev., iii. 251). 



Ft. Bras., Piperac., Anat. The author con- 3 Mem. sur la Fam. des Piperacees ; Prodr., 



firmed what was already known of the general 235 65 . 



structure of the stem. Studying this and that of 4 Ung., Ueb d. Bau. &c. — C. J. de Cordem., 



the root in Peperomia, Piper, Artanthe, Chavica, in Adansonia, iii. 2S6. This author found that 



Tildenia, he found that the medulla was traversed in the young stem, at first cellular, there ap- 



by fibrovascular bundles. The stem of an peared " twelve fibro-vascular bundles, which 



Artanthe revealed a score in transverse section, soon united into eight, by the symmetrical junc- 



most widely scattered towards the centre. In tion of eight in adjacent pairs." 



the wood there were medullary rays of various 5 Schleid., in Linneea, xi. (1837), 530; 



generations, and dotted vessels. Orundz., i. 250 ; ii. 54, 142. 



2 Sec also on this point : Link, Ic. Anat., ix. 



