BV JOHN SHIRLEY AND C. A. LAMBERT. 607 



from this latest-formed cam])ium consists of 6-8 rows of lii-ick- 

 like, tbin-walled cells, outside of wliich is a single-rowed circle 

 of sclerencb\'ma. 



(b.) BouGAiNViLLEA LATERITIA Hort., (Plate Ixv., fig. 1 1 ), differs 

 little from Z>. spectabilis and B. tSatideriana, except that numer- 

 ous sacs containing clinorhombic crystals — raphides — are found 

 in the periderm and pith. Where a bud is formed on the stem, 

 the tissues entering the bud from the stele are full of these 

 needle-crystal sacs. 



(c.) BouGAiNViLLEA Sanderiana Hort., (Plate Ixv., fig.l2).— 

 This section ( x 90) shows the central and first-formed vascular 

 bundles isolated in the pith, as in the case of its allies; and four 

 annual zones of alternating wood, bast, and encircling medullary 

 ray-tissue. This last might be taken for cambium, but is quite 

 distinct in the character of the cells composing it, from that of 

 the last-formed cambium-ring. Periderm, cork, and the dead 

 cells of the outer bark are well shown. 



(d.) Piper nigrum Linn., (PI. Ixvi., fig. 13). — The general struc- 

 ture of this stem is similar to that of Bougainvillea. The first- 

 formed set of bundles, seven in number, develops cambium within 

 each bundle, but not between them. These bundles are further 

 isolated by the growth of the pith. Circumferential ly, other 

 cambium-tissues form, making a complete wavy ring, and give 

 rise to a normally developed set of vascular bundles of the usual 

 dicotyledonous arrangement. Lying in the pith, outside each 

 of the original isolated bundles, is a resin-duct; and a larger one 

 occupies the centre of the stem. Bounding the outer, normal 

 ring of vascular bundles on the inner side, is a complete wavy 

 ring of sclerenchyma, of about six irregular rows of thickly 

 strengthened, polygonal cells. An indefinite ring of sclerenchyma, 

 its cells elongated circumferentiall}', surrounds the outer ring of 

 wood and bast. 



Stephania HERNANDiiEFOLiA Walp. — In a first year's shoot, 

 there is a remarkable similarity between the cells of the pith, 

 medullary rays, and periderm. As in Piper nigrum, the stele is 

 bounded by a scolloped line, outside of which new cambiums 

 arise, and new ringS of wood and bast are developed. 



