598 LECTURE XXII. 



The simplest mode of vegetative reproduction is that 

 which obtains among unicellular plants of low organisation. 

 When the cell which constitutes the body of the individual 

 has attained by growth its limit of size, it gives rise, by some 

 form of cell-division, to one or more new cells, which then 

 grow, and, becoming separated from one another, constitute 

 one or more new individuals similar to the original organism. 

 Good examples of this are afforded by the lowly organised 

 unicellular Algae and Fungi. This mode of vegetative re- 

 production is merely a process of cell-division essentially the 

 same as that which takes place in the - growing members of 

 multicellular plants, with this difference, however, that whereas 

 in a multicellular plant the products of cell-division remain 

 coherent and add to the number of the cells of which the 

 plant consists, in a unicellular plant the products of division 

 separate and thus come to constitute new individuals. 



Vegetative reproduction also takes place to a greater or 

 less extent in plants of higher organisation. In the simplest 

 case, parts of the body, not specially modified, become sepa- 

 rated from each other, and each may constitute a new indi- 

 vidual. For instance, it commonly happens in Mosses that 

 the main stem gradually dies away from behind forwards, so 

 that the lateral branches become isolated, and each of these 

 then comes to be an independent Moss-plant. In fact, under 

 artificial conditions, almost any part of a plant may subserve 

 vegetative reproduction. For instance, the stem, the leaves, 

 the rhizoids, or the sporogonium, of a Moss may be induced 

 by appropriate cultivation to give rise to filamentous pro- 

 tonema on which new Moss-plants are developed as lateral 

 buds. Again, a great number of our garden-plants are pro- 

 pagated by means of " cuttings" ; that is, a shoot is removed 

 from a plant and is induced to develope roots and thus to 

 constitute a complete plant. In the case of \some of the 

 Begonias artificial propagation is effected by inducing adven- 

 titious budding on portions of isolated leaves, each bud de- 

 veloping into a new plant. 



In a great number of plants vegetative reproduction is 

 effected by means of specially modified embryonic shoots or 



