24 HOUGH'S AMERICAN WOODS. 



throughout, and set closely along the summits of the ridges are clusters 

 of very sharp stout radiating spines sometimes 2 in. or more in length, 

 and effectually protecting the green epidermis of the plant behind 

 them. 



HABTTAT. The Saguaro is found in western Arizona, south of the 

 Colorado plateau, southward throughout southern Arizona west of 

 San Pedro river, and southward into Mexico. Its sentinel-like trunks 

 are curious objects of interest to travelers crossing southern Arizona, 

 where it is found in dry gravelly soil and among rocks where few 

 other plants can maintain existence. 



PHYSICAL PROPERTIES. The Saguaro trunk consists of a frame 

 work of fibro- vascular bundles in the form of a circle of poles at a 

 little distance apart, and enveloped in a soft juicy parenchymatous 

 tissue which also forms the center of the stem. 



The arrangement of the tissues of these stems we have found we are 

 able to show in our sections much better than anticipated at the outset. 

 We expected the soft tissues would not hold together, but found them 

 amply strong. In decomposition of the stems the soft tissues soon 

 disintegrate, leaving the frame work cluster of poles, which are strong 

 but very light, with conspicuous medullary rays radiating from the 

 innermost side, and with annual layers of growth quite distinctly 

 marked. The wood of these poles is of a light yellowish brown, and 

 when perfectly dry have a specific gravity of 0.3188, a cubic foot 

 weighing 19.87.* 



USES. The woody poles are used for the rafters of adobe houses, 

 for fencing, and by the Indians for lances and bows. The fruit is an 

 article of food for the Indians and is also eaten by certain birds. 



ORDER OAPRIFOLIAOEJE: HONEYSUCKLE FAMILY. 



Leaves opposite and mostly without stipules. Flowers perfect, 4-5 numerous; 

 calyx-tube coherent with the ovary; petals united, forming a tubular or rotate 

 corolla; stamens inserted in the corolla and usually as many as its lobes; pistil 

 with inferior 2-8-celled ovary containing two to many anatropous ovules. Fruit 

 a berry drupe or pod; seed with small embryo and fleshy albumen. 



Order composed mostly of shrubs, a few trees and a few herbs. 



GENUS SAMBUCUS, TOURNEFORT. 



Leaves unequally pinnate, destitute of stipules, leaflets serrate, pointed; leaf- 

 buds scaly; branchlets stiff and containing large pith, flowers small, regular and 

 perfect (rarely polygamous), articulated with small pedicels, in broad terminal 

 compound cymes; calyx-tube adnate to the ovary, with 3-5 broadly spreading 

 lobes; corolla with 3-5 equal lobes broadly spreading, white (or tinted with yellow 

 or red); stamens 5, inserted on the corolla, alternate with its lobes; stamens with 

 extrorse versatile 2-celled anthers, attached by the back and opening longitudi- 

 nally; pistal with mostly inferior 3-5-celled ovary, short thick style and terminal 



* Sargent's Silva, vol. V, p. 54. 



