346 PKOF. H. M. WAED AND MISS E. DALE ON CRATEROSTIGMA PUMILUM. 



In thick sections, less highly magnified, the colouring-matter appears to be lying 

 freely Id the spaces ; hut on closer examination it is seen to consist of minute rounded 

 granules or drops, closely packed on the outer walls of the cells to which they are 

 attached. 



The cells of the piliferous layer are thin-walled, with the exception of a few of rather 

 smaller size in which the outer w^all is thickened (PL XXXV. fig. 18). On most of the 

 roots there are extremely few root-hairs. 



A radial lon^'itudinal section shows that the intercellular spaces form passages hounded 

 by cells which appear to lie in rows and to have a more or less moniliibrm outline 

 (PI. XXXV. fig. 18). 



In oblique tangential sections the spaces between the cells in one plane appear to 

 alternate with those separating the cells which lie immediately below. In such a section 

 the colour is seen lying on the surfaces of the walls, and the large amount of it is very 

 striking. 



The colouring-matter is not present between the two outer rows of cells, even where 

 the cells of the piliferous layer and that immediately within it are not in uninterrupted 

 contact with one another. 



It has been said (p. 343) that the ends of the larger roots and of some of the smaller 

 ones are colourless. A longitudinal section in this region shows that, although the spaces 

 are continuous almost to the apex, the red granules usually end some distance behind the 

 tip, in most cases suddenly. Near the end of some roots the colour is present in patches 

 separated from one another by areas free from granules. 



The cells of the cortex in the root contain considerable numbers of colourless bodies, 

 which are evidently leucoplasts (leucoleucites). With iodine they become purple owing 

 to the presence of starch, and are therefore to be regarded as amyloplasts. 



If a plant be taken out of the ground and placed in water w ith its roots exposed to the 

 action of light, the leucoplasts become green, i. e. they are changed into chloroplasts 

 (chloroleucites). 



The Stele.— 'rh^re is nothing specially noteworthy, as departing from ordinary types, 

 in the stele. In the centre are thielr-walled sclerenchymatous fibres, in many cases still 

 retaining their cell-contents. They are surrounded by about six groups of xylem, 

 alternating with as many groups of phloem, separated from one another by small 

 parenchymatous cells, the whole being enclosed by a not very definite pericycle and 

 endodermis (PI. XXXV. fig. 17). Immediately beyond the endodermis are cortical cells 

 separated by spaces containing the colour-granules. 



A longitudinal tangential section near the outside of the stele shows, even in extremely 

 small roots and in fresh or hardened material, a central group of elongated thin-walled 

 cells with very sinuous longitudinal w^alls. The most external of these cells, on each 

 side, have always their inner walls sinuous and their outer walls smooth. These cells 

 may perhaps be regarded as endodermal {cf. De Pary, ' Comparative Anatomy of the 

 Phanerogams and Perns,' fig. 50, p. 123). 



The Leaf.~A transverse section near the base of the leaf consists of rounded cells 

 of approximately equal size, separated from one another by very irregular spaces 



