MOEPHOLOGY OF REPEODUCTIVE OEGANS 95 



zygote gives rise to a rudimentary sporophyte ; in others to a 

 gametophyte. 



We may now examine separately the vegetative, asexual, 

 and sexual reproductive mechanisms. 



Section I. 



VEGETATIVE REPRODUCTIVE STEnCTUEES. 



Vegetative reproduction is the simplest manner of producing 

 a new individual, and can in the lower forms often be hardly 

 distinguished fcom ordinary growth. It can be illustrated by a 

 series of examples. In the lowest Fungi and Algae, in which the 

 plant consists only of a single cell, as in Yeast, an outgrowth 

 from the cells appears, which becomes detached and forms a 

 new individual, giving rise to others in turn. Sometimes the 

 process is so rapid that the new cell gives rise to another before 

 being detached, and this may go on till a chain of cells is 

 formed. Each of these is, however, an independent Yeast 

 plant, and the separation is a mere matter of time. This 

 process is known as budding. In other cases, as in the Desmids, 

 the cell divides into two, each of which, by subsequent growth, 

 becomes a new individual. This is only slightly different froni 

 the first process, and is known a.B fission. 



In more highly differentiated plants certain portions of the 

 parent are detached, which develop into the adult forms. These 

 are generally known as geminis, and may be unicellular or 

 multicellular. Instances are found of the former among the 

 AlgsE ; of the latter in higher groups also, particularly the Liver- 

 worts and Mosses, where they are developed in special places. 

 In the former group they are found in cup-like receptacles upon 

 the upper surface of the thalloid stem ; in the latter their 

 position varies greatly. In the Lichens smaU portions of the 

 thallus are set free ; these are known as soredia. They have the 

 same structure as the thaUus itself. 



In many plants frequently branches become independent by 

 the perishing of the main axis on which they arise. In the 

 case of the Eunner of the Strawberry a bud is developed on the 

 stem which puts out roots and attaches itself to the ground. 

 Then the stem on which it arises perishes, and the new plant 

 lives for itself. Other cases of similar behaviour are furnished 

 by the production of bulbs or corms in many plants, and in the 

 behaviour of many rhizomes. 



Cuttings illustrate the same mode of reproduction. A piece 



