377 



in the grain and, therefore, should not be subjected to too much weight in the 

 case of beams, &c., but is an excellent timber for joinery and finishing work 

 generally. Mr. P. MacMahon states, " That it has always been regarded as the 

 most valuable of Queensland Pines, but it is unfortunately becoming scarce; and 

 although it seems to be readily culti^'able, or can be readily produced with 

 reasonable protection, supplies are not obtainable in anything like the quantity 

 that they were some time ago." 



Transverse Tests of Timber, Agathis robusta. 

 (Standard size, 38 in. x. 3 in. x 3 in.) 



Size of specimen in inches 



Area of cross section, square inches ... 



Breaking load in lb. 



Modulus of rupture in lb. per square inch 



,, elasticity ,, ,, 



Rate of load in lb. per minute 



No. I. 



63-03; 03-03 



9-12 



3,600 



6,990 



970,786 



300 



No. 2. 



No. 3. 



B 3 -03 



; D 3-03 



9-12 



3.500 



6,796 



900,000 



437 



B304; P302 



9-18 



3,800 



7,366 



911,250 



345 



(b) Anatomy. 



Both radial and tangential sections present microscopical features charac- 

 teristic of the species and genus, and form good lines of demarcation between it and 

 the cognate genera. 



The pitted cells are found on the radial walls in alternating rows, 

 generall}- in threes, but occasionally in fours, as against a single row in the cor- 

 responding space of the Callitris and Podocarpiis, and having the appearance of a 

 tessellated pavement or mosaic, a character, however, in which it much resembles 

 the Avaucavias. (Figures 265-6.) 



These elongated colonies of pits form conspicuous figures in the radial 

 sections, and show an affinity between the xylems of Araiicaria and Agathis, the 

 latter, however, having more frequentty four rows. HoUick and Jeffrey, (" Amer. 

 Nat." Vol. XL, No. 471, pi. 5, Figure i), show two rows of pits occurring in 

 Brachyphylhmi macyocarpum, Newb., a fossil timber from Staten Island, N.Y. 



The medullary rays are composed of narrow parenchymatous cells more 

 often not containing any manganese compound substance, whilst cells of the 

 xylem tracheids are also devoid of this substance, a feature still further emphasised 

 in transverse sections, Figures 261-2, and one that differentiates the timber from 

 Arancaria. The rdcys are not many cells high, and only one broad. 



The large number (up to twelve) of simple cells between the walls of the 

 lumina is also a good diagnostic character of the genus. 



