124 IX. THE DICOTYLEDONOUS STEM HERBACEOUS TYPES. 



about i inch apart, bending down the ends as a handle, and 

 cutting sections through the short middle portion; or, take a 

 piece about ^ inch long, stick a needle through it near one side, 

 hold it thereby flat on the index-finger, and cut sections. If the 

 section cuts radially through a vascular bundle, as it should do, 

 we can see in it, passing from the inner edge outwards, the 

 narrow annular and spiral vessels (vascular tracheides), then the 

 pitted ducts, between them elongated wood parenchyma, then 

 the thin-walled elongated cambium cells, the sieve-tubes and 

 companion-cells, and at both edges the sclerenchymatous elements 

 of the sheath. If our section is laid in chlorzinc iodine we shall 

 notice reddish grains in the sieve-tubes. These are starch grains 

 which contain amylo-dextrin, and which the sieve-tubes appear in 

 this case to be richly provided with. 



Latex-vessels of Chelidonium. The vascular bundle of the 

 Great Celandine, Chelidonium majus, is so similarly constructed 

 to that of Ranunculus repens, that the cross-section will be at once 

 understood. Assuming that our section is from alcohol material, 

 we shall note in it, however, many cells with dark-brown contents 

 in the bast of the bundle, on the inner limits of the xylem, and in 

 special number on the flanks and at the outer edge of the arc of 

 sclerenchyma which covers the bast portion of the vascular 

 bundle, and singly also in the ground-tissue between the bundles. 

 These contents consist of the orange-red milk or latex of Cheli- 

 donium, coagulated in alcohol, and the cells in question are so 

 striking that it is impossible to overlook them. They are all 

 thin-walled, even those which are inserted in the outer edge of 

 the sclerenchyma string ; they are not otherwise distinguished by 

 any special form. These latex-vessels or laticiferous-vessels 

 can be found very easily also in radial longitudinal sections, being 

 recognised at once by their yellowish-brown contents. They 

 present the appearance of long tubes running approximately 

 parallel to the long axis of the stem. Without difficulty the 

 existence of cross- w^alls in these tubes can be determined. These 

 cross-walls are more or less clearly pierced in their centres by one 

 or several pores ; they are wanting, however, here and there, 

 where we should expect to find them, since they may have been 

 completely dissolved. Lateral communications of the latex- 

 vessels cannot be observed in Chelidonium. If the stem used be 

 at all thick, the latex-vessels can be even more readily found 

 in longitudinal tangential sections, in which, by reason of their 



