SOME FEATURES IN THE ANATOMY OF THE 
SAPINDALES*’ 
RutH HOLDEN 
(WITH PLATES II AND III) 
In studying the phylogeny of plants, there are certain general 
principles upon which all conclusions- are based. One of these 
deals with the retention of ancestral characteristics. A striking 
example of this is afforded by the anatomy of the cycads. The 
vegetative stem of these forms always has exclusively centrifugal 
metaxylem, but in the leaf petiole, the metaxylem is predominately 
centripetal, with only a slight development in a centrifugal direc- 
tion. Centripetal wood structure is, of course, the more primitive, 
and its appearance in the leaf petiole of the Cycadales serves to 
relate them to their extinct Cycadofilicean ancestors, where centripe- 
tal wood was present in the stem. Similar bundles with centripe- 
tal wood are present also in the reproductive axes of certain 
Cycadales.? 
Another well known seat of primitive conditions is the root, good 
examples of which are furnished by the Abietineae. The first and 
older subtribe, the Pineae, is characterized by the invariable presence 
of resin canals in the normal wood of both root and stem, while in 
the more modern subtribe, the Abietae, resin canals are generally 
absent in the normal wood of the stem. Resin canals do occur, in 
all four genera of the Abietae, in the center of the primary wood 
of the root.3 
Recent investigations have shown that ancestral conditions may 
be recalled as a result of wounding. For example, these resin 
canals, present in the roots of the Abietae, are present invariably 
Contributions from the Phanerogamic Laboratories of Harvard University, 
no. 42. 
2 Scott, D. H., The anatomical — presented by the peduncle of Cycada- — 
897. 
ceae. Ann. Botany II2399-419. Pls. 
3 Jerrrey, E. C., The comparative pea: and phy schol the Coniferales. 
II. The Abietineae. Mem. Boston Soc. Nat. Hist. 6:1-37. pls. 19 
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