122 



MINUTE STRUCTURE OF THE STEM. 



3G7. The cribrose portion of a collateral bundle often has, in 

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

 as cambiform cells. 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 



99 



cells may divide bj* transverse partitions, and if the cells are 

 moderately large the last divisions may be parenclvymatous. In 

 most monocotyledons and dicotyledons the cribrose-cells are much 

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

 guished b} T being less sharply quadrangular. In many succulents 

 there are also veiy 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 Morphologie und Anatomic 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 commnnis: r, parenchyma of the primary 

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

 grains; the fibro-vascular bundle is made up of the phloem b, //, the xylem g, t, and the 

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

 soft bast ?/, 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.) 



