552 TWO PRINCIPAL MODES OF REPRODUCTION. 



CHAPTEE XV. 



OF REPRODUCTION. 



723. THERE is no one of the functions of living beings, that 

 distinguishes them in a more striking and evident manner 

 from the inert bodies which surround them, than the process 

 of Eeproduction. By this function, each race of Plants and 

 Animals is perpetuated ; whilst the individuals composing it 

 successively disappear from the face of the earth, by that 

 death and decay which is the common lot of all. A very un- 

 necessary degree of mystery has been spread around this pro- 

 cess. It has been regarded as one altogether inscrutable, 

 whose real nature could not be unveiled, even by the scientific 

 inquirer, and whose secrets the uninitiated should never seek 

 to comprehend. But so much light has been thrown upon it 

 by recent investigations, that we now know at least as much 

 of this, as of almost any other function ; and the Author's ex- 

 perience has led him to believe that such knowledge may be 

 communicated to the general reader, without the least in- 

 fringement of the purest delicacy of feeling. In his own 

 judgment, indeed, it is far better to afford a legitimate satis- 

 faction to the curiosity which naturally exists upon the sub- 

 ject, than, by refusing all information, to drive the inquirer 

 into objectionable methods of gratifying it. 



724. It has been elsewhere shown (YEGET. PHYS., Chaps, 

 ix., XIL), that, in the Vegetable Kingdom, there are two 

 distinct modes by which the propagation of Plants may 

 take place ; the extension of the parent structure into new 

 portions, which, being independent of it and of each other, 

 can maintain their lives when separated from it ; and the 

 origination of a new being by the concurrent action of two 

 sets of cells set apart for this special function, and desig- 

 nated " sperm-cells " and " germ-cells." The bodies of the 

 first class are known as leaf-buds or gemmae in the Flowering 

 Plants, and sometimes also among Cryptogamia, some of which 

 last, as the Marchantia (VEGET. PHYS. 757), are fur- 

 nished with a peculiar means of producing them ; and it 

 appears from recent investigations that the " spores " of Ferns, 



