XLni] ANATOMY 135 



pointed out, tracheids with horizontal patches of resin may be 

 mistaken for resiniferous parenchyma; but true parenchyma 

 occasionally occurs^. 



Attention has been called to the diagnostic value of the hori- 

 zontal thickening bands which on staining, and often in fossil 

 wood, stand out as conspicuous features on the tracheids of the 

 great majority of Conifers (fig. 693, C). Many authors speak of 

 these bands as bars of Sanio^, apparently overlooking the fact that 

 this term (Sanio's 'Balken') was used by Miiller* for the horizontal 

 bars previously described by Winkler* on the tracheids of Araucaria 

 brasiliensis (fig. 693, I). Groom and Eushton^ have also called 

 attention to the inaccurate use of the term Sanio's bars and they 

 suggest the more appropriate expression Sanio's rims for the 

 persistent margins of the primordial pit-areas which appear as 

 horizontal lines between the bordered pits. An American author 

 goes so far as to claim that 'by far the most reliable criterion for 

 diagnosing coniferous wood is the occurrence of the bars [rims] 

 of Sanio^.' But if, as Jeffrey and his pupils assert, Sanio's rims 

 are present on the tracheids of all Conifers except the Araucarineae 

 the diagnostic value of this feature is exceedingly small. Jefirey' 

 has shown that in the first-year wood of Araucaria and in the cone 

 of A. Bidwillii the pits are not always contiguous and rims of 

 Sanio may then be present. Moreover, as Thomson^ states, the 

 darkly stained lines between contiguous pits on some Araucarian 

 tracheids (fig. 691, F) may be regarded as feebly marked rims of 

 Sanio. It is not surprising that in the case of tracheids with 2 — 3 

 series of contiguous hexagonal pits, which leave no free surface', 

 Sanio's rims are not represented i". 



The most recent contribution to our knowledge of the rims of 

 Sanio is by Mr Sifton" who describes them in petioles of Cycas 



1 Jeffrey (12) p. 536. ^ Gerry (10). 



= MuUer (90). ■■ Winkler (72). 



* Groom and Rushton (13). See also Rushton (16). 



« Holden (13)p. 252; (13^). ' Jeffrey (12) PI. vi. fig. b. 



8 Thomson (13) p. 22. » Gothan (10) p. 32. 



^° In a recent paper entitled 'Gliding growth and bars of Sanio' (Grossenbacher. 

 Amer. Journ. Bot. vol. i. no. 10, 1914) the expression ' bars of Sanio ' is employed in 

 an unusual sense and not in accordance with the ordinary usage of the term bars, 

 or rims, of Sanio. 

 " Sifton (15). 



