CRYPTOGAMS 339 



a mass of spores, mingled with elongated filaments called 

 elators, which, by their elastic movements, assist in dissem- 

 inating the spores. These latter, on germinating, produce, 

 not a simple sporophyte like that which bore them, but 

 the thallus of the liverwort with all its complicated arrange- 

 ment of antheridia and archegonia and vegetative organs 

 that seem to foreshadow, by the analogies they suggest, 

 the coming of the higher plants. 



394. Sexual and asexual reproduction. We find here 

 a very marked change from the simple reproductive processes 

 observed in the algae and fungi. In the forms thus far con- 

 sidered, this function was carried on mainly by simple vege- 

 tative fission or budding, with a more or less irregular in- 

 tervention of resting spores. If only one kind of spore is 

 concerned, reproduction is said to be asexual. When two 

 different kinds of cells, the egg and sperm cell, unite to form 

 an oospore, as in the liverworts, reproduction is said to be 

 sexual. While sexual reproduction takes place to some 

 extent among both algse and fungi, the prevailing method 

 among thallophytes is asexual, and may be carried on in 

 three different ways : by fission (and budding), by resting 

 spores, and by conjugation. 



Representing the plant body by A and the resting spores 

 by a, the primitive asexual processes may be expressed to 

 the eye by the accompanying formulas : - 



(1) Fission and budding : A >A >A >A > 



(2) Resting spores : A a->A a^>A a-> 



(3) Conjugation : A + A -+a->A + A -*--> 



In (3), as was seen in the conjugating cells of the spirogyra 

 (342), the method is a little more complicated, showing an 

 approach toward the sexual process. In each of these cases, 

 however, there is only one kind of cell concerned, while in 

 the liverworts there are not only different kinds, techni- 

 cally known as gametes, but specialized organs, archegonia 

 and antheridia, for producing them. The thallus body 

 bearing these organs is termed the gametophyte, because it 



