164 



Botanical Periodicals. 



Hferous manner, {fig. 65.) For the sake of our inexperienced readers, we 

 shall give Doctor Hooker's description : — 

 ** Joints (j^g. 65. a to b) from 4 in. to 6 in. in 

 length, oblong, remarkably compressed ; vary- 

 ing in breadth, from 1 in. to 5 in. ; the margins 

 slightly thickened, crenato-iobate, everywhere 

 glabrous. There is a distinct mid-rib {fig. 66. c) 

 running through the centre of these, and bun- 

 dles of vessels forming lateral thickened nerves 

 or ribs, leading off 

 from it, and extend- 

 ing in a curve, 

 whose convexity is 

 uppermost {d) to 

 the crenatures. The 

 colour of the plant 

 is rather a dark 



green, the ribs and margin often reddish. 

 Flowers {fig. 66. e) numerous upon the joints, 

 solitary in each crenature, small, and not unlike 

 those of the Rhlpsalis tribe. The base is occu- 

 pied by the germen (/), which is nearly sphe- 

 rical, pale green, and smooth. Calyx (g) of 

 three small, oval, concave, brownish, scariose 

 leaflets, but gradually becoming larger and more 

 petaloid, and passing almost insensibly into the five pale yellowish-green 

 spreading petals (7^); tube none. Stamens (i) numerous, inserted within 

 the united bases of the calyx and corolla. Filaments {h) rather longer 

 than the corolla, and white. Anthers (/) didymous, yellowish white. Style 

 {m) filiform, as long as the stamens; stigmas (w) four, or generally five, 

 linear, recurved, pubescent, white. 



Dioscoreo! [Pedadus Dioscorides^ a Greek physician) cinnamomifolia, the 

 Cinnamon-leaved Dioscorea, or Yam, is a native of the woods about Rio de 

 Janeiro, also sent to this country by Mr. Harrison. It deserves the atten- 

 tion of the young naturalist, not only as being the potato of tropical climates, 

 but as having the male and female flowers on difTerent plants, and conse- 

 quently belonging to the class Dioe'cia (</w, twice, oi/f05, a house) of Lin- 

 naeus, and to the order of this class Hexandria, as having six stamens. 

 Sprengel, and other moderns, however, who propose not to take the cir- 

 cumstance of the sexes being in difTerent plants, into consideration in form- 

 ing the classes, but to be guided entirely by the stamens and pistils, refer 

 Dioscorea to Hexandria Monogynia. This genus and one or two others 

 form a natural order of themselves, the type of which being Dioscorea, the 

 order, in conformity to a fundamental rule, 

 alluded to (p. 36.), is called Diosc6re<^. Only 

 the male plant [fig. 67.) is yet known. 

 The following is its description by Dr. 

 Hooker. " Root a roundish, ill-shapen 

 tuber, as large as the human head. Stem 

 (a) twining, branched, striated, pubescenti- 

 hirsute, hairs brownish : whole plant destitute 

 of prickles ; leaves alternate, petiolate {b\ 

 oblongo-acuminate, quite entire, of a texture 

 between coriaceous and fleshy, shining, hav- 

 ing three distinct nerves or ribs (c), which 

 are prominent on the under side, where the ' 

 leaf is of a paler green, and where, near the 

 Ipase, are some dark dots of glands : the 

 margin itself, when held between the eye 



