146 



SECRETORY RESERVOIRS. 



cylindrical. As the internode extends, the length of the cells and of the raphides increases; 

 till in the case of the cells it exceeds their breadth on an average 3-4 times. Hitherto a 

 thin protoplasmic layer, with a nucleus of sharp contour, lines the delicate cellulose wall. 

 As the internode extends further, the cells which remain thin-walled, become 10-20 times 

 longer than they are broad, the protoplasmic parts disappear, while round the bundle 

 of raphides there is seen only transparent mucilage, which shrinks greatly but without 

 turning misty in alcohol, swells quickly in water till it is unrecognisable, turns yellow 

 with Schultze's solution, and is not dissolved in potash. Meanwhile the raphides do not 

 increase perceptibly in number or size, they form henceforth a relatively small group in 

 the sac filled with hyaline mucilage. According to Hanstein the members of such a 

 series of sacs coalesce, at least frequently and partially, to continuous long tubes, by the 

 breaking down of the transverse cellulose walls which separate them. But the observa- 

 tions cited in evidence of this are not sufficient to substantiate it. It is true it is often 

 found in longitudinal sections that the raphides are irregularly displaced, and have bored 

 through the delicate transverse walls of the series of sacs ; but on the other hand sacs are 

 also found closed at both ends, and dense bundles of raphides in them. And one can 

 often directly see the displacement of the raphides and the perforation .of the transverse 

 walls in progress before one's eyes. The action of water produces this result, the 

 mucilage swells in fundamentally the same way as in solitary raphide-containing sacs. 

 I could not prove to myself the occurrence of spontaneous perforation of the transverse 

 walls, that is of a coalescence of the series to a continuous tube or ' Vessel.' Where I 

 found a perforation already present, it was a gaping rent, such as is seen to be formed 

 when the wall bursts. Further, it is not impossible to suppose that even in the living plant, 

 when too much water is present, walls may burst, and so the same phenomena appear as 

 are seen in sections. According to all these data, which coincide in the main with the' 

 statements of Hanstein, the structures in question may be regarded as nothing more than 

 a special kind of raphide-containing sac distinguished by form and arrangement. 



Rosanoff' was the first to find in the pith of Kerria japonica, Ricinus com- 

 munis, in the sacs which accompany the vascular bundles of the petiole of Aroideae 

 (e. g. Anthurium rubricaule, Selloum, Pothos argyrea, Philodendron Sellowianum), 

 as well as in the parts of the flower of Encephalartos and Nelumbium, that groups of 

 crystals are connected with the membrane ; either their apices are in close contact 

 with the lateral wall, or they are suspended by bars of cellulose, which extend from 

 the wall into the cavity, as far as single points of the group ; these bars are often 

 branched, and often hollowed like tubes. De La Rue found a similar attachment in 

 the parenchyma of the leaf of Hoya carnosa in the case of small groups of crystals, 

 contained in cells which have protoplasm and even chlorophyll (these, however, in 

 the strict sense do not belong to this category), and also in the leaf and petiole of 

 Aroidese (Pothos crassinervis, &c.). Further, Pfitzer ", following up an older observa- 

 tion of Schacht ', showed that the large solitary klinorhomhic crystals contained in the 

 foliage of Citrus, and those in the cortex of Salix aurita, Populus italica, Celtis 

 australis, Fagus sylvatica, Rhamnus Frangula, Acer opulifolium, and Platanus 

 orientalis, are closely surrounded by a cellulose skin, a large part of the surface of 

 which is attached to the cellulose wall of the sac : this skin arises from the protoplasm 

 of the young crystal-bearing cell, which surrounds the crystal : at first it lies free, 

 later it becomes firmly attached to the cell wall. At the point of contact the lateral 



1 Botan. Zeitg. 1865, p. 329.— Ibid. 1867, p. 41.— Compare also De la Rue, ibid. 1869, p. 537. 



" Flora, 1872, p. 95, Taf. III. 



' Abhandl. Senkenberg. Gesellsch. z. Frankfurt a M. I. p. 150, Taf. VII. ,fig. 21. T . 



