22 INTRODUCTION. 



111. The albumen is a storage, outside of the embryo, of food for the 

 young plantlet. It is principally of a starchy nature and may be beside 

 of the embryo, but usually completely envelops it. It is always found in 

 seeds where the space and function are not taken up by the embryo itself, 

 and its relative quantity may accordingly be little or very great. In tex- 

 ture it is extremely various, as it may be oily, mucilaginous, fleshy, fari- 

 naceous etc. It is quite horn like in coffee, where it constitutes by far 

 the greater part of the seed the kernels of commerce. In the cocoanut 

 it is fibrous, hollow, and filled with "milk," while the embryo itself is 

 very small. In the seed of the Ivory Palm it is quite like ivory and con- 

 stitutes the " vegetable ivory " of commerce. All these forms of hard 

 albumen soften at the time of germination. A seed of the Basswood, 

 with quite copious albumen and entirely enveloping the embryo, is seen 

 in Fig. 41-9. 



112. Seeds containing no albumen are said to be exalbuminous, in dis- 

 tinction from the albuminous seeds, i. e., those containing albumen. 



113. An Aril is an adventitious growth outside of and partly or 

 wholly enveloping the seeds of certain plants. The mace of the nutmeg 

 is of this nature. The seed of the White Water- Lily is invested in a 

 transparent aril, and those of the Climbing-Bittersweet and Burning 

 Bush in scarlet arils. 



THE PHYSICAL PROPERTIES OF WOODS. 



114. These, so far as relating to the woods of North America north 

 of Mexico were very carefully studied, with the exception of a few 

 species, in connection with the United States census investigations of 

 1880. The special agent employed for this purpose was Mr. Stephen P. 

 Sharpies, of Cambridge, Mass., who conducted elaborate experiments in 

 their determination, and the results, fully tabulated with explanations of 

 the methods employed, were incorporated by Prof. Chas. S. Sargent in 

 Vol. IX [Ninth Census of the United States, 1880]. It is from that 

 report that we have taken the estimates of Specific Gravity, Percentage 

 of Ash, Relative Approximate Fuel Value, Coefficient of Elasticity, Modu- 

 lus of Rupture, Resistance to Longitudinal Pressure, Resistance to 

 Indentation and Weight of a Cubic Foot in Pounds. These, with the 

 methods employed, we will here briefly explain, quoting largely from the 

 report above referred to. A given estimate represents the average of all 

 the results obtained in that particular line of experimenting. 



115. The Specific Gravity. At least two determinations were made 

 for each species studied, and, in case of woods of commercial importance, 

 specimens were taken from many trees growing in widely different parts 

 of the country and under different conditions of soil and climate. . The 

 specimens used were made 100 millimeters long and about 35 millimeters 

 square, and were dried at 100 centigrade until they ceased to lose in 

 weight. The specific gravity was then obtained by measurement with 

 micrometer calipers and calculation from the weights of the blocks. Of 

 the four hundred and twenty-nine species experimented upon, the range 

 of variation was found to be from 0.2616 (in Ficus aurea, the small- 

 fruited Fig), to 1.3020 (in Condalia ferrea, the Black Iron-wood). 



