122 Fossil Botany, 



with the peculiar substance formed by the plant, and contained 

 in the descending sap. Thus a Poppy would saturate th 

 water with a flavor of opium, and a Spurge would give it a 

 acrid taste. The theory of Endosmose has given rise to con 

 siderable discussion among botanists, and some have used 

 strong arguments in opposition to its truth. Our limits forbid 

 more than a bare statement of the principle on which it de- 

 pends. 



Roots appear to have a certain power of selecting the proper 

 matter for their nourishment, and will absorb some substances 

 in the fluid around, and reject others. If a stalk of Wheat, 

 and a Pea, grow in the same soil, the former will absorb all 

 the silex, or flinty matter which the water can dissolve, and 

 this is deposited in the stem. On melting a wheat straw with 

 the blowpipe, there will remain silex enough to form a glass 

 bead, and in some other grasses, as the Bamboo, it is often 

 collected in the joints, in large masses, and in the Rattan, it is 

 so abundant as to turn the edge of the best tempered knife. 

 The Pea, on the other hand, will reject this, and confine its 

 selection to calcareous substances, or those formed of lime. As 

 to the nature of the fluid absorbed by roots, their food, and the 

 manner in which they are nourished, we shall speak hereafter. 



FOSSIL BOTANY. 



NUMBER THREE. 



Fossil remains of plants are found in various conditions; 

 sometimes little changed in their appearance. Sometimes 

 their substance is completely saturated with mineral matter, 

 and yet both the external and internal structure completely 

 preserved. There are fossil trees which so nearly resemble 

 decayed wood, that the utmost scrutiny cannot detect the dif- 

 ference, until the weight and hardness are ascertained. In 

 some cases, the most delicate tissue of the original is to be seen, 

 and is most distinctly and beautifully displayed. The husks. 

 and shells of some fruits, the cones of the pine and fir, the 



