66 Reproduction and Meiosis 



Plant morphologists have frequently called the first meiotic 

 division the heterotypic division, or division different from a 

 typical mitosis, and the second meiotic division the homeotypic 

 division, or division like a typical mitosis. In number of 

 chromosomes involved and in the position of the arms of the 

 "split" chromosome in prophase, however, this second meiotic 

 division differs from a somatic division. 



Vegetative Reproduction 



In higher plants various vegetative methods of reproduction 

 may be found by which a new plant may arise from a piece of 

 one of the vegetative organs of another. Such asexual methods 

 of reproduction may be the only usual methods in some plants, 

 and in many plants they may be of great importance from an 

 agricultural viewpoint. 



If plants reproduce by a vegetative method, whether from 

 roots, stems, or leaves, all the new plants will be exactly like 

 one another and like the parental plant. A group of plants 

 produced vegetatively from one original plant is called a clone. 

 All the plants of a given clone are alike. 



Hermaphrodites 



In many animals and some higher plants, each individual is 

 either male or female; but in some animals and most higher 

 plants, both sexes are represented in each individual. Organisms 

 in which one individual contains both male and female sex organs 

 are known as hermaphrodites. In some hermaphroditic ani- 

 mals, like Hydra, the sperm of one animal will fertilize the eggs 

 of the same animal; but in the earthworm, the eggs must be 

 fertilized by sperm from a different animal. When an her- 

 maphroditic animal or plant produces a new individual by the 

 union of egg and sperm from the same parent, such an organism 

 is said to be self -fertilized; but when the gametes are from dif- 

 ferent individuals, such an organism is cross-fertilized. Many 

 seed plants have elaborate mechanisms to ensure that they will 

 be cross-fertilized, peas and others are regularly self-fertiUzed, 

 and still others may produce seeds by either self- or cross- 

 fertilization. 



