340 Transactions. 



2. Peperomia EvMicheri (P. Urvilleana of Hooker, 20) is a small creep- 

 ing, succulent herb. Grows in damp woods, on rocks, less often on trees. 



3. A second Peperomia, which is probably identical with the Pepe- 

 romia reflexa of Australia and many tropical countries, is not very common 

 in New Zealand, and was not obtainable for investigation. 



Anatomical Features. 

 Stem. 



The woody stem of Macropiper excelsum shows the double ring charac- 

 teristic of the woody Piperaceae. In a transverse section we find on the 

 outside periderm ; beneath is cortical tissue. A young stem shows a 

 distinct epidermis, the cells of which are more or less oblong in outline ; 

 immediately below are from 2 to 3 rows of cells, showing tangential divi- 

 sions. It is from these we have the periderm. 



Below the epidermis, or periderm, is well-marked collenchyma, espe- 

 cially thick behind the bundles. De Bary refers to a similar structure 

 in Piper rugosum : :i The hypodermal layer surrounds the whole stem 

 as a distinct closed, multiseriate (collenchymatous) layer." The collen- 

 chymatous layer consists of from 8 to 10 layers, narrowing to less layers 

 with slightly wider elements between the bundles. 



Immediately beneath this is a discontinuous ring of sclerenchymatous 

 elements, one or two elements wide, abutting at places on the vascular 

 bundles ; longitudinal sections show these elements to be branched occa- 

 sionally. 



Then comes the outer ring of bundles, each bundle separated by a wide 

 medullary ray from its neighbour. The bundles of this ring show secondary 

 thickening to a marked degree. On the inside of this ring is a sclerenchy- 

 matous band several layers thick, broken occasionally between two bundles 

 (fig. 2). 



In the centre of the stem is medulla, in which is a ring of separate 

 bundles. In stems % in. to 1 in. broad there are about 10, but the 

 number varies in accordance with the size of the stem ; 3 to 4 is common 

 in young parts, especially seedlings. 



On the outside of each bundle both of the outer and often of the inner 

 ring are much-thickened sclerenchymatous elements. Then there is the 

 inner sclerenchymatous band. De Bary, remarking on the inner scleren- 

 chymatous band, says, " The converse case, that a continuous layer of 

 sclerenchyma supports the whole inner side of the ring of vascular bundles, 

 is rare in Dicotyledons. This is the case in the woody Piperaceae — Artanthe, 

 Chavica sp." 



In some stems — Ranunculus repens, for instance — we find sclerenchy- 

 matous elements on both sides of the bundle, representing a sheath. It 

 is probable that in the Piperaceae these sclerenchymatous elements repre- 

 sent the bundle-sheath, which has become much thickened and extended 

 on the inner side for mechanical purposes. There is sclerenchyma to the 

 inside of each bundle of the medullary circle, but it does not form a con- 

 tinuous ring ; also at the base of the stem, and in young branches coming 

 from the base, as in fig. 6a, in seedlings the continuity of the ring disappears, 

 all which lends to the view that the sclerenchymatous ring is an extended 

 sheath. 



The phloem consists of several layers showing deeply staining sieve-tubes, 

 and companion cells ; sieve-plates, where cut through, show very fine pits. 



