434 TRANSACTIONS AND PROCEEDINGS OF [Sess. lvi. 



we have instead a group of cells similar to a tannin-sac 

 group but containing only protoplasm. Similar elements in 

 neighbouring rows do not in most cases correspond in position 

 so as to form concentric circles, but rather alternate with 

 each other. 



The fibres are rectangular in cross section with the longer 

 diameter directed tangentially, and about twice the length 

 of the radial diameter ; the tangential walls are concave 

 outwards, while the radial walls are convex, — both are con- 

 siderably thickened and provided with somewhat wide pits. 



The sieve-tubes ar-e also rectangular in cross section and 

 of the same tangential dimension as tlie fibres, but are 

 much .compressed in a radial direction. They are provided 

 with a single row of distinct circular or elliptical sieve-plates 

 on their radial walls. 



In Dacrydium cujjressinum the arrangement of the phloem 

 in alternate cylinders is scarcely recognisable, and the tannin- 

 sacs form tangential groups of four to ten cells rather than 

 concentric cylinders extending round the stem. 



The structure of the individual tannin-sacs is also quite 

 different from that seen in D. Fraiiklinii. They do not form 

 vertical groups as in that species, but each group is repre- 

 sented by a single large spindle-shaped cell which is much 

 swollen, and consequently very irregular in outline. Generally 

 the radial walls by which the neighbouring cells press 

 against one another are fiat, while the tangential walls are 

 convex outwards. At those points where the tannin-sacs 

 are crossed by medullary rays they are considerably con- 

 stricted in l)oth lateral dimensions, and not unfrequently 

 they send out along the course of the rays, generally towards 

 the centre -of the stem, long blind diverticula which end in 

 more or less sharp points. The tangential walls are slightly 

 and equally thickened all over, as are also the walls of the 

 radially directed diverticula, and botli contain large numbers 

 of miimte ciystals of calcium-oxalate. The radial walls, on the 

 other hand, are crossed at intervals by transverse bands of 

 thickening matter which, wider at the margin than at the 

 centre, leave large circular or broadly elHptical interspaces on 

 which no thickening has taken place. Tliese cells, at least 

 in the adult state, contain neither nucleus nor protoplasm, 

 but are completely filled with tannin. 



