1 1 2 The Rev. P. Keith on the Internal Structure of Plants. 



galvanic action by certain weights of particular bodies, is pre- 

 cisely the same with that which is required to separate them 

 from their combination with other particles when subject to 

 electrolytic action. He describes one experiment in parti- 

 cular, in which " the chemical action of about 32 parts of 

 zinc, arranged as a voltaic battery, was able to evolve a cur- 

 rent of electricity capable of decomposing and transferring 

 the elements of 9 grains of water*." Here we may remark the 

 difference in expression, while the fact stated is the same. If 

 for electricity we say iodine, the quantity " set free," or 

 " called into action," during the decomposition of an atom of 

 iodide of zinc, is precisely the same which is required " for 

 forming a new compound on the decomposition of an atom of 

 water." I am aware that the once prevalent doctrine of the 

 materiality of caloric and electricity has given way before the 

 conclusions deduced from certain optical phacnomena; but if 

 the being subject to similar laws of combination with material 

 bodies has no weight in restoring them to a place among 

 forms of matter, it may still assist us in investigating others of 

 their relations. 



XIX. On the Internal Structure of Plants. By the liev. 



Patrick Keith, F.L.S.f 

 "PROM the previous survey of the vegetable structure J, it 

 -■- appears that the organs into which the plant is externally 

 distinguishable are the root, trunk, branches, buds, leaves, 

 flower, and fruit, or seed. These we may call decomposite 

 organs. But the organs which are thus discoverable by ex- 

 ternal inspection are each and all of them reducible to com- 

 ponent parts, which we will call composite organs, and which 

 are again resolvable into constituent parts also, that is, into 

 primary or elementary organs, the detection and exhibition 

 of which are the ultimate object of the researches of the vege- 

 table anatomist. 



Decomposite Organs. 

 The Seed.— In the dissection and anatomy of the seed, no 

 botanist has been so successful as Gaertner. His work De 

 Seminibus et Fructibus Plantarum, a work meritorious beyond 

 all praise, is the best guide to the knowledge of carpology, 

 and is to be studied in conjunction with the actual inspection 

 and analysis of seeds. Seeds are divisible into two parts, di- 

 stinguishable without much difficulty, namely, the integuments 



* See Lond. and Edinb. Phil. Mag., vol. iv. p. 294, 295.— Edit. 



+ Communicated by the Author. 



j See Lond. and Edinb. Phil. Mag., vol.iii. p. 78, and 1 20 etscq.— Edit. 



