584 TRANS. ST. LOUIS ACAD. SCIENCE. 



in y. Bermudiana it is said to be similar but harder; in all the 

 others, the wood of which I could examine, it is paler red or 

 yellowish, harder and less fragrant; they split less readily, but 

 are, in the regions where they abound, not rarely the most avail- 

 able and highly esteemed firewood. 



The leaves of young plants or of vigorous shoots are, it is 

 well known, acicular and arranged in alternating whorls of threes 

 (rarely in twos), quite similar to the permanent leaves of the 

 yumpers of the section of Oxycerfrus, but the older and especially 

 the fertile plants have very short, mostly closely imbricate, almost 

 scale-like leaves, the lower part more or less adnate to and form- 

 ing part of the branchlet itself. These leaves occur in some spe- 

 cies in pairs, in others usually in threes, so as to form 4- sided or 

 6-sided branchlets, but this arrangement is not constant and ought 

 not to be much relied on for specific characters. The leaves bear 

 their stomata on the concave, upper, oppressed side ; the lower, 

 convex side or back has no stomata, but is marked by a more or 

 less distinct, either prominent or sunken "gland," as it is called: 

 the dorsal and only resin-vesicle or duct of the leaf. This is glo- 

 bose or oblong according to the shape of the leaf, or rarely (in 

 y. Bermudiana) elongated, and lies in some close to the epider- 

 mis, or is in others separated from it by a layer of parenchyma- 

 tous cells. The contents of this resin-vesicle are in some species 

 or in some localities excreted through the epidermis, and are apt 

 to appear on the back of the leaves as an aromatic balsam, and, 

 later, as condensed resin. 



The edges of the leaf are rarely entire, mostly delicately denti- 

 culate, or irregularly fringed with minute, corneous, often curved 

 processes. This character permits us to distinguish species where 

 others may fail. 



In the figure on the next page the form and proportions of the 

 leaf-margin of the different species is represented as it appears 

 when magnified 280 times ; but a much lower power, even a 

 good glass, in a favorable light, will enable the student to recog- 

 nize its character. The figures show that only y. Virginiana and 

 Bermudiana have entire leaves, while y. Californica has the most 

 marked fringe ; the other species are intermediate between these 

 extremes. 



Of the old world Sabince, which I have examined, only y. 



