VEGETABLE CYTOLOGY 71 



Free Cell Formation. This is a type of reproduction in which the 

 nucleus and protoplasm become separated into two or more masses 

 each of which forms a cell wall about itself. Seen in formation of 

 ascospores within ascus of Ascomycetes and spores within spore cases 

 of molds. 



Rejuvenescence. In this mode of reproduction the protoplasm 

 of the cell becomes rounded out, escapes by rupture of the cell wall, 

 forms cilia and moves about as a zoospore. Later it looses its cilia, 

 develops a cell wall and passes into a resting condition. Under 

 favorable circumstances it grows into a new organism. It is found 

 in (Edogonium, Ectocarpus, etc. 



There are two kinds of sexual reproduction, viz. : Conjugation and 

 Fertilization. In both of these the sexual cells called gametes or 

 their nuclei come together and their protoplasm blends to form a 

 new cell. This is the common method seen in higher plants. 



Conjugation. A union of two gametes, alike in character, the 

 product being a zygote or zygospore. This method of reproduction is 

 seen in the molds, Spirogyra, Zygnema and Diatoms. 



Fertilization. A union of two unlike gametes or their nuclei, the 

 product being an oospore. One gamete, the male sexual cell, is 

 smaller and active, while the other, the female sexual cell, is larger 

 and passive. This process is seen among the higher and many of 

 the lower plants. 



INDIRECT NUCLEAR DIVISION (MITOSIS OR KARYOKINESIS) 



This is the general method of division seen in the formation of 

 tissues of higher plants. 



The process begins in the nucleus and ends with the formation of 

 a cell wall dividing the new- formed cells. 



When we examine a cell in its resting stage we find the nucleus 

 more or less spherical in shape, surrounded by a nuclear membrane 

 and containing a nuclear network, nuclear sap and one or more 

 nucleoli. The nuclear network consists of a colorless network of 

 limn adhering to which are numerous minute granules called chro- 

 matin which take the stain of a basic dye. Surrounding the nucleus 

 is the cytoplasm. 



As the cell commences to divide, the nucleus elongates and the 



