ON THE OCCURRENCE AND SIGNIFICANCE OF “BARS” 
OR “RIMS” OF SANIO IN THE CYCADS 
H. B. S1FToN 
(WITH PLATE XV) 
The “bars” or “‘rims’’ of Sanio were probably first figured by 
GO6ppERT (2) in 1849, as has been pointed out by Miss GERRY (1). 
SANIO (7), however, did not, as she states, claim to be the dis- 
coverer of them, although he was the first to describe them at all 
adequately, and hence they have borne his name. In studying 
the development of the wood cells in Pinus silvestris, he found 
thickened rings, complete or incomplete, which grew up around 
thin spots in the cellulose primary. walls. The thin areas he 
designated as the “‘ Primordialtiipfeln,” and on these bordered pits 
were formed. The thickened rims, or “‘Umrissen,” of these areas 
are the structures that have until recently been known as the 
“bars of Sanio.” In 1913 Groom and RusHTon (3) applied the 
name “rims” to them. This term is descriptive of Santo’s theory 
of their method of formation and serves to distinguish them from 
trabeculae. 
Until the last few years they did not come into much promi- 
nence, but in several recent papers they have been considered of 
great importance. Miss Gerry, in the paper mentioned above, 
gave a comprehensive account of their distribution in the conifers. 
She found them in all the members of this group except the arau- 
carians, whose wood structure could in this way be distinguished 
from the other forms. She also suggests the extension of this 
distinction to the fossil forms, as the following sentence indicates: 
“The distribution of the bars of Sanio . . . . establishes a con- 
stant and useful diagnostic character in the determination of fossil 
woods” (p. 122). She would associate all the fossil conifers which 
have the ‘‘rims” with the Abietineae, and those which do not 
exhibit them with the Araucarineae, regardless of other character- 
istics of their tracheary structure. 
Botanical Gazette, vol. 60] [400 
