314 GENERAL BOTANY 



male or a female plant. This physiological differentiation of spores 

 in Equisetum is very important, since it indicates how those spore 

 differences probably originated which gave rise to the so-called 

 heterosporous plants, of which we shall learn in our later studies. 



GAMETOPHYTE AND EMBRYO 



The male and female gametophytes of the equiseta resemble 

 those of the ferns, except that they are more highly branched 

 (Fig. 180). The male plants are small and bear the male sex 

 organs at the ends of the lobes or on the margins of the 



Sporophyte 



Spore Gametophyte '.'(& " Sporangia 



germination Gametophytes Sex organs Gamete* Zygote and sporophyte % liji and spore 



Gametophyte Sporophyte 



FIG. 180. Diagram showing life history of Equisetum 



gametophyte. The female plants are larger than the males and 

 bear the female gametangia on a thickened, cushionlike portion 

 of the gametophyte beneath green, lobelike extensions of its 

 upper surface. The male and female sex organs (.antkericUa and 

 archegonia) and the gametes indicate by their structure and form 

 their close relation to similar reproductive cells and organs of 

 the ferns. Fertilization takes place by means of motile male 

 gametes, which are liberated in films of water formed by rain 

 or dew. Fertilization of the female gamete is followed by the 

 development of a parasitic embryo sporophyte, as in the ferns. 

 Embryo. The general form and structure of the embryo 

 sporophyte in the equiseta is determined by the kind of adult 

 sporophyte into which it is destined to develop. We find as a 



