iqiq] bailey— bars of SANIO 451 



to indicate that he considered these parallel curved lines as outHnes 

 of a heavily embossed or thickened rim. 



Strasburger (15) showed very clearly that in Pinus and Larix 

 Sanio's doppelten Umrissen may be the outhnes of embossed 

 portions of the middle lamella. In other words, he made it evident 

 that when the primary pit areas are close together they are sep- 

 arated by a single transverse thickening, but that when they are 

 not closely approximated there may be two curved thickened 

 strips, separated bv a less heavily embossed area, between them 



(fig. 5). 



Miss Gerry (3), in discussing the distribution of bandlike 



thickenings of the middle lamella in the Gymnospermae, referred to 



them as follows (p. 119): 



The "bars" or "folds" of cellulose which when stained with haematoxylin 

 are especially obvious as horizontal or more or less semicircular markings in 

 the tracheide walls of a radial section from such a conifer as Pinus silvestris 



L. were described by Sanio in 1872 These structures were named 



"Bars of Sanio" from him 



Groom and Rushton (5), who have studied the structure and 

 chemical composition of the bandUke thickenings of the middle 

 lamella in Indian species of Pinus, state: 



According to Samo's work it is these unoccupied margins of the primary 

 areas that coincide in position with the above-mentioned bands that are seen 

 in radial section. Consequently the name " Sanio's rims " may be given to the 



structures causing the bandlike appearance When the primary pit 



areas are in contact, the two contiguous Sanio's rims are naturally "fused" 

 and form a band that is transverse and single, except possibly at the two lateral 

 edges where the natural curv^ature of each original boundary of the area causes 



the band to fork In radial sections with iodine and sulphuric acid the 



"rims" stain yellow; with ordinary haematoxylin they remain unstained; leav- 

 ing sections in cupra-ammonium to dissolve out any cellulose, their staining 

 properties are not changed materially. They are not composed of cellulose. 

 .... When young the actual marginal portion of the primary pit area does 

 not thicken by deposits of lignified wall as soon as it does elsewhere (except on 

 the pit-closing membrane), but thickens by successive deposits of pectic 

 substance until a stage is reached when lignified wall-substance is deposited 

 even over the now thickened rims of the primary pit area. Sanio's rims repre- 

 sent a system of rodlike or bandlike pectic thickenings of the middle lamella 

 running transversely in the radial walls and linked here and there by slightly 



