SOME FEATURES IN THE ANATOMY OF THE MALVALES.^ 
C. C. FORSAITH 
In the study of the phylogeny of plants there are certain general 
principles upon which conclusions are based, among which the law of 
recapitulation is of the utmost importance. This law in its application 
to plant anatomy shov/s that primitive conditions are found in the 
seedling and in the first annual ring of growth. Furthermore, inves- 
tigation has shown other primitive regions, viz., the root, the leaf 
petiole, and the reproductive axis. Experimental work has also dem- 
onstrated the value of traumatic regions. Studies in these directions 
have shown that the root is the most conservative, while the stem is 
the most progressive region of the plant, and consequently this latter 
organ loses its ancestral characters sooner than any other. It has 
further been shown that of these organs, the leaf petiole and repro- 
ductive axis are more progressive than the root, but not so much so 
as the stem, w^hich makes them valuable as localities of transitional 
tendencies. Lastly, but by no means of the least importance, is the 
region of injury. 
Many examples might be cited in illustration of these general 
principles taken from the anatomical features of the Conifers, an ex- 
ceptionally favorable group for studies of this nature, owing to the 
abundance of fossil material of ancestral forms. One exemplification 
will serve. Pinus is considered to be the lowest genus of the Abieti- 
neae, a group in which resin canals appear normally in the woody 
cylinder, but in Abies, and other of the Abietineae, resin canals do not 
normally develop in the wood of the stem, but are found in the xylem 
of the root and other conservative organs, as well as in traumatic 
regions, thus illustrating the principles of retention and reversion. 
Since it has been somewhat generally admitted by competent investi- 
gators that the Abietae have been derived from the true pines, or 
Pineae, the natural inference is, that the conditions found in these 
conservative regions, just mentioned, may be taken as phylogenetic 
evidence of ancestral conditions (i). Still further illustrations of 
1 Contributions from the Phanerogamic Laboratories of Harvard University, 
No. 66. 
238 
