‘ Sanio s Bars' in Finns Inops. 425 
a direction at right angles to its main axis is transmitted from the two ends 
to the middle, so that the rod becomes hollow along its whole length. 
At the same time the rod becomes thicker by means of deposits on it 
of layers of wall-substance (which in tracheides assumes the form of lignified 
material and in phloem cellulose). Such a deposit recalls the mode of 
centripetal thickening of pegs and the like projecting in from the walls of 
Caulerpa , and the projections in the mesophyll of Pine needles and other 
plants, also the deposit of cellulose on hyphae of a parasitic fungus 
traversing a living cell whose protoplasm is responsible for the cellulose in 
question. This explanation explains the continuity of the Sanio bars 
throughout successive tracheides and sieve tubes, the growth in thickness, 
the origin of the central hollow, and the final shape of the mature bar, but 
there is no clue to the original inception of the bar in the cambium cell. 
Summary. 
1. Sanio’s bars are small rods crossing the tracheides, cambium, and 
phloem elements in many Conifers. 
2. In phloem and cambium the walls are of cellulose, whilst in the 
xylem region they are lignified. 
3. In cambium the bars exist as thin solid rods, and in the xylem and 
phloem as more or less hollow rods. 
4. Small masses of protoplasm frequently surround the rods in the 
cambium cells and suggest a possible mode of origin. 
In conclusion, I wish to convey my best thanks to Professor Percy 
Groom, of the Imperial College, for his help and profitable suggestions 
during the progress of the investigation, and to Mr. A. W. Hill, Assistant 
Director of the Royal Botanic Gardens, Kew, for allowing me to have 
specimens of Pine woods from the Kew Collection. 
Literature cited and referred to. 
1. C. Sanio : Vergleichende Untersuchungen liber die Elementarorgane des Holzkorpers. Bot. 
Zeit., 1863, p. 1 1 3. 
2. H. von Mohl : Morphologische Betrachtung der Blatter von Sciadopitys. Bot. Zeit., 1871, p. 12. 
3. C. Winkler: Zur Anatomie von Araucaria brasiliensis. Bot. Zeit., 1872, p. 582. 
4. E. Russow : Ueber den Bau nnd die Entwicklung der Siebrohren, sovvieden Bau und die Entwick- 
lung der secundaren Rinde der Dikotylen und Gymnospermen. Bot. Centralblatt, 1882, 
p. 419. 
5. de Bary : Comparative Anatomy of Flowering Plants and Ferns. Clarendon Press, 1884, p. 163. 
6. C. Muller : Ueber die Balken in den Holzelementen der Coniferen. Berichte d. Deut. Bot. 
Gesell., Bd. viii, 1890, pp. 17-45. 
7. W. Raatz : Die Stabbildungen im secundaren Holzkorper der Baume und die Initialentheorie. 
* Pringsheim’s Jahrb. f. wiss. Bot., vol. xiii, 1892, p. 567. 
8. P. Groom and W. Rushton : Journ. Linn. Soc., Bot., vol. xli, 1913, p. 457. 
G g 3 
