;352 ERNES']' WARKKN. 



and the annual rings are not very sharply marked. The 

 s]iecimen consists of two pieces of different stems, one being 

 about 6 inches in diameter and the other about 4 inches. In 

 both pieces the pith and protoxylem are present. 



Description. — Pith, diameter of the rounded cells about 

 0"037 mm. The pith cells bordei-ing the protoxylem are 

 somewhat flattened (text-fig. 1, C), Outside the pith there 

 is a variable number of spiral vessels varying in diameter 

 from 0'30 to 0'042 mm. 'i'hey may be rounded or somewlig^t 

 hexagonal in cross-section. The spiral thickening may be 

 irregular so that the vessel tends to be reticular in character 

 as is shown in the innermost vessel in the figure. The I'ow of 

 dark dots bordering tlie edge would appear to be an optical 

 effect of seeing the spiral thickening in profile. 



Outside the spiral vessels there may be a variable number 

 of rows of more or less vertically elongated cells, those 

 nearer to the vessels being shorter than the outer ones. In 

 these the walls are thinner than in the tracheides. They 

 may be regarded as wood parenchyma. A much narrower 

 vessel was observed in one of the sections in the midst of 

 this tissue. In the figure a medullai-y ray is seen extending 

 inwards to the pith. In the neighbourhood of the pith the 

 medullary cells tend to be of irregular shape. 



The elongated cells between the spiral vessels and tracheides 



Text-fig. 1. 



A — X -00. Radial section of Dadoxjlon (probably D. austral e 

 Aber). Uiiikomaas Valley. Natal Coal Measures. Mus. No. 219. 

 Aiitnnm and spring traclieides are shown. The cells of the 

 npj)er niednllary ray apparently contained resin. Pits are close 

 set. and tend to be hexagonal. 



B. — X '200. Radial section of Dadoxylon (probably D. australe). 

 Natal. Mus. No. 11. Pits are generally scattered; Ijut in some 

 parts of the same section they are much more closely packed than 

 here rej)resented. 



C. — X "200. Radial section of Dadoxylon (probably D. australe) 

 through ]3ith and protoxylem. Natal. Mus. No. 11. It m;iy be 

 noticed that the pits of the tracheides are more closely set than in 

 Fig. B. 



D. — X 200. Radial section of Dadoxylon sp. Dannhauser. Natal 

 Coal Mea>^nres. Mus. No. 160. The pits between the medullary 

 cells and tracheides are mostly solitary and large. 



