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A TEXTBOOK OF THEORETICAL BOTANY 



takes place during the autumn and spring, and affords a very rapid and 

 successful means of dispersal during the growing season. 







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Fig. 384. — Marcfuhitia polyniorpha. Development of 

 gemmae showing stalk formed by basal cells. 



Sexual Reproduction 



Marchantia polyniorpha is dioecious, that is to say, that the male and 

 female reproductive organs are borne on different plants. The sex organs 

 are generally produced during the summer, and differ markedly from those 

 of Pellia. Instead of being immersed within the tissues of the thallus, the 

 sex organs are elevated upon special branch structures, termed respectively 

 the antheridiophore, which bears the male organs, and the archegonio- 

 phore, which bears the female organs. Both structures are developed at the 

 growing apex and form a direct continuation of the midrib, but they grow 

 vertically upwards through the apical indentation in the thallus until they 

 are as much as 3 cm. in height. In general structure these organs resemble 

 the thallus, and we must regard them as branches of the thallus, borne on 

 the end of stalks, rather than as purely reproductive bodies. 



The Antheridiophore 



The antheridiophore consists of a stalk bearing at its apex a disc-shaped 

 cap (Fig. 385). In transverse section this stalk is seen to consist of a narrow 

 thallus branch, the margins of which are curled downwards and inwards 

 until they almost meet below the midrib, thus forming two vertical channels 

 running up the stalk (Fig. 386). 



The disc is made up of eight separate lobes, the indentations between 



