[ '^9 ] 



No. 7. 



THE LIGNITE OF WASHING BAY, CO. TYEONE. 



By T. JOHNSON, D.Sc, F.L.S., 

 Professoi- of Botany, Eoyal College of Science for Ireland, 



AND 



JANE G. GILMOEE, B.Sc. 

 (Plate III.) 



[Read June 27. Printed August 28, 1922.] 



Lignite or brown coal was fonnd at various depths of the bore in isolated pieces 

 embedded in the white clay ; at a depth of 999 feet the deposit became a black 

 mass. Much of the wood was very much crushed and twisted, to obliteration of 

 its coniferous character, but for resin and a few pits. 



Some scraps occur at 712 feet, 869 feet 6 inches, and at 909 feet, which are 

 flaky, and have the appearance of charred wood. These pieces show the structure 

 of the pits on the walls of tracheids and of the medullary rays better than the 

 sections obtained from the solid pieces. The pits on the walls of the tracheids 

 and the medullary rays are the same as in the solid material, but no resin 

 parenchyma is found, with the exception of one piece at 909 feet. It seems that, in 

 the charring, from whatever cause, the resin disappeared. 



Although Dicotyledonous leaves are plentiful in the bore, no trace of 

 Dicotyledonous wood has been observed. Goeppert (6) recorded the same fact 

 with regard to the Tertiary Flora of Silesia. 



The cross-section (PI. Ill, figs. 1, 2) shows the wood much cnrshed and 

 somewhat disorganized. The growth rings are very narrow, varying from 

 200 to 400;i ; an occasional broad ring is seen. The spring wood consists of 10-.30 

 rows of tracheids, which are fairly broad; the average size is QOju; occasionally they 

 reach 80ju, and in one case 100^ in diameter. They are thick-walled, and much 

 flattened by pressure. The autumn wood occupies about a third of the ring. 



The bordered pits (PL III, figs. 3, 4, 5, 6) have a circular pore, but are 

 frequently somewhat flattened top and bottom or are horizontally extended in 

 their outer contour. They are in single or double rows ; frequently three rows 

 occur, and in one tracheid four rows of pits were seen (PI. Ill, fig. 6). When in 

 two or more rows, they are opposite, and may be either closely packed or scattered. 

 They measure 20-24(U in diameter, and when flattened measure about ifi less. 

 Between the rows of bordered pits are very distinct Sanio's bars, which are 

 sometimes double. On the tangential walls of the spring and autumn tracheids 

 small bordered pits are common (PI. Ill, fig. 7) on the whole extent of the wall. 

 Accordmg to Penhallow (14), pitting in this position is a primitive feature, and 

 among recent Conifers is best seen in Sequoia gigantm, making it in this respect 

 almost unique. 



Eesin canals are wanting. Eesin parenchyma is very plentiful, and scattered 

 throughout the wood. The average breadth of a resin cell is 50-60ju, and the 



SOIENT, PEOO. K.D.S., VOL XVII, NO. 7. K 



