212 INTERCELLULAR SPACES. 



of Canna, Maranta, Phrynium, Thalia), the leaves of many Bromeliacese, e.g. B. 

 Caratas : cells, branched in a stellate manner in all directions, with long arms, and 

 small central portion, form the inner part, the ' pith ' of the halm of many species of 

 Juncus : similar stellate cells, but with a large bladder-like central portion, compose 

 the massive lacunar inner cortex of the Rhizome of Scirpus lacustris, Sparganium 

 ramosum, &c. 



In Dicotyledonous water-plants, stellate lacunar parenchyma is rare, with excep- 

 tion of the tissues of foliage leaves ; still, according to Duval-Jouve, it composes the 

 diaphragms of the air-passages of Limnanthemum nymphoides, and, according to 

 Planchon ^ and Trecul -, those of Nelumbium ; also the spongy cortical mass of the 

 roots of species of Jussiaea, and of the internodes of the stem of Mimosese, which 

 serve these plants as floats. 



The spongy air-containing cortex of the adventitious roots, which spring from the 

 nodes, and which serve as floats for those branches of amphibious species of Jussisea 

 (J. repens, J. grandiflora, J. natans, J. hehninthorrhiza) which grow in water ^, consists of 

 3-6 armed cells. They are arranged in concentric layers, and each puts out at least 

 three narrow cylindrical arms from a not distended central portion. Of these the 

 longest is horizontal and directed radially towards the periphery, and its end is connected 

 with the opposite face of a cell of the next outer layer. The two shorter are in the 

 simplest case radially and tangentially vertical, and of equal length, so that the radial 

 view of the cell has the form of a procumbent H . The end of each is connected with 

 the corresponding one of the next upper or lower cell of the same layer. A connection of 

 the cells of a layer in a tangential direction is finally brought about, sometimes by single 

 tangential arms, sometimes by oblique direction of the halves of the cross-bar of the T. 

 Radial and transverse sections thus show between the narrow arms very large, four- 

 cornered air-cavities, which are continuous one with another. The length of the arms 

 and of the air-cavities is nearly equal in each of the concentric layers, and increases suc- 

 cessively from within outwards. The radial arms of the outermost layer abut directly 

 on the epidermis, which soon breaks away and collapses. Also the spongy cortex of 

 Desmanthus natans W., and apparently other similar Mimoseae, may be here described, 

 though from its mode of origin it should be ranged under secondary formations. The 

 internodes of the stem of this plant, which grow horizontally in the water, are, accord- 

 ing to Rosanoff ■', at first cylindrical; their parenchymatous outer cortex consists of an 

 inner part, which is composed of 3-4 layers of roundish rather large parenchymatous 

 cells, and an outer consisting of 3 small-celled layers covered by the epidermis. When 

 the extension of the internode is ended, it swells to a shape like a barrel as the result of 

 the appearance of the spongy floating apparatus. The formation of the latter begins 

 with tangential divisions of the third layer of parenchyma from without, which, together 

 with the changes which follow, are then continued successively in the more internal 

 layers. The cells formed by the tangential divisions are arranged in radial rows, and 

 grow to irregular stellate sacs with narrow cylindrical arms, while the central portion is 

 not distended : the ends of the arms remain connected ; the cells thus enclose wide 

 lacunae filled with air. Each second or third radial row is branched, and connected 

 especially in the tangential direction, the i or 2 rows between them are branched on all 

 sides. The epidermis and the hypodermal parenchyma are torn into narrow rags by the 

 spongy swelling. Later the whole spongy apparatus is thrown off as bark. 



1 Flore des serres, torn. VI. ^ Ann. Sci. Nat. 4 ser. I. p 168. 



^ Ch. Martius, Sur les racines aeriferes des especes aquatiques' des Jussirea, Mem. Acad, de 

 Montpellier, torn. VI (1866). — Frank, Beitr. z. Pflanzenphysiologie, p. 152, fig. 24. 

 * Botan. Zeitg. 1871, p. 829, Taf. X. 



