122 MINUTE STRUCTURE OF THE STEM. 



367. The cribrose portion of a collateral bundle often has, in 

 addition to true cribrose-cells, prismatic, thin-walled cells, known 

 as cambiform cetts. 1 



368. According to Vochting 2 the cambiform and cribrose cells 

 appear in some cases to have a common mother-cell, which di- 

 vides obliquely in the direction of its length. The cambiform 



cells may divide by transverse partitions, and if the cells are 

 moderately large the last divisions may be parenchymatous. In 

 most monocotyledons and dicotyledons the cribrose-cells are much 

 larger than the cambiform ones, and their cross-sections are distin- 

 guished by being less sharply quadrangular. In many succulents 

 there are also very small cells resembling undeveloped cribrose- 

 cells. 



369. The cribrose and woody parts of a collateral bundle are 

 generally distinguishable from each other by the lignified char- 



1 De Bary reserves for these cells the term Cambiform, which was used by 

 Nageli in a wider sense. 



2 Beitrage zur Morphologic und Anatomie der Rhipsalideen, Pringsheim's 

 Jahrb., 1874, p. 327. 



FIG. 99. Transverse section of a part of the central cylinder of the mature hypocoty- 

 ledonary portion of the stem of Ricinus communis: r, parenchyma of the primary 

 cortex; m, of the pith; between rand b is the simple endodermis containing starch- 

 grains; the fibro-vascular bundle is made up of the phloem b, y. the xylem ft, t, and the 

 cambium c, c ; cb, interfascicular cambium. In the phloem are the bast-tibres 6, b, the 

 soft bast y, y (partly parenchyma and partly cribrose-tubes); in the xylem, small pitted 

 ducts t, t, wider pitted ducts g, g, and between them wood-fibres. (Sachs.) 



