304 Vegetable Physiology. 



being destitute of calyx or corolla, or both. The fruit usualk 

 contains a viscid matter, which in some species is made into 

 bird-lime. 



The well known Mistletoe, (Viscum album,) once used in 

 the superstitious rites of the old Druids, and still hung up at 

 Christmas in every country-house in England, is the most noted 

 plant of the order. Its roots insinuate their fibres into the wood 

 of various kinds of trees, and from them springs a pendant 

 evergreen bush, from two to five feet in diameter, covered in 

 winter with small white glutinous berries. Several species of 

 Loranthus are among the most beautiful of tropical flowers 

 hanging in splendid scarlet clusters from the trees, which are 

 thus clothed with a beauty not their own. 



VEGETABLE PHYSIOLOGY. 



NUMBER EIGHT. 



JERATION OF SAP. 



A chemical change of great importance is effected on the 

 sap when it is subjected by the le/ives to the action of li<rht. 

 It consists in the decomposition of the carbonic acid gas, which 

 is either brought to the leaves by the sap itself, or obtained 

 directly from the surrounding atmosphere. In either case its 

 oxygen is separated and disengaged in the form of gas; while 

 its carbon is retained, and composes an essential ingredient of 

 the altered sap, which, as it now possesses one of the princi- 

 pal elements of vegetable structures, may be considered as 

 having made a near approach to its complete assimilation. 



Two glass jars were inverted over the same water-bath ; the 

 one filled with carbonic acid gas, the other filled with water, 

 containing a sprig of mint; the jars communicating below by 

 means of the water-bath, on the surface of which some oil was 

 poured, so as to intercept all communication between the water 



