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ANATOMY 



133 



and occasionally three or even four, rows (fig. 691, H); they are 

 circular and not contiguous and the pits of a double row are as a 

 rule on the same level ; they are opposite and not alternate. This 

 type of pitting occurs also in all the other families except the 

 Araucarineae though in Agathis opposite pits are not unknown ^ 

 (fig. 691, D) and Conwentz^ states that he has seen separate and 

 circular pits in the tracheids of recent species. The occasional 

 occurrence of pits in clusters and not in opposite pairs has been 

 described in Pinus Merkensis^ : this is a feature characteristic of 

 the tracheids of some fossil types, e.g., Cedroxylon transiens Goth. 

 In Agathis and Araucaria there may be 1 — 3 rows and as many 

 as 5 rows on the tracheids of cone peduncles (fig. 691, A). The 

 pits are contiguous and flattened, and those of adjacent rows are 

 alternate and hexagonal*. Thomson has called attention to the 

 occasional occurrence, especially in the region of the rays, of 

 transversely elongated or scalariform pits in the tracheids of 

 Araucaria. A single series of flattened pits and 

 even the occasional occurrence of alternate hexa- 

 gonal pits are not infallible criteria of an Arau- 

 carian affinity : in Dacrydium the pits of a double 

 row may be alternate though rarely contiguous, 

 and this is the case in some other genera, while in 

 Saxegothaea^ (fig. 692) the pits are as a rule uni- 

 seriate and often flattened. Worsdell^ describes 

 circular and separate pits in the cone-scales of 

 Araucaria and Thomson records alternate bi- 

 seriate pits in the cone-axis and early wood of 

 the Abietineae. Flattened pits are described in 

 Podocarpus poly sf achy a'' and I have seen similar 

 pits in the wood of Torreya calif ornica and several Fig. 692. Tracheids 

 other conifers other than the Araucarineae. The 1^^^^^° "^(ITter 

 size of the bordered pits though worthy of notice stiles.) 

 is not in itself a feature of much value. As Nicol 

 first pointed out, in Araucaria they are larger than in Taxus ; in 

 Pinus they are larger than in Araucaria: Kraus^ speaks of the 



1 Jeffrey (12) PI. vi. fig. b. ^ Conwentz (92) p. 35. 



' Groom and Rushton (13). 



* Tor good figures, see especially Thomson (13). 



* Stiles (08). . « Worsdell (99). ' Gerry (10). « Kraus (83). 



