THE ALGAE 153 



When the carpospores are mature the spore wall bursts and the naked 

 protoplasmic mass escapes, comes to rest, develops a new w^all and germinates 

 into a pad or sole of parenchymatous tissue, from which develop numerous 

 shoots of a simple filamentous plant. This plant is spoken of as the 

 Chantransia stage on account of its resemblance to another Alga of that 

 name. Terminal cells on the lower branches of these filaments function as 

 apical cells, and from them fresh Batrachospermum plants arise. They may 

 also arise directly from the sole. 



Asexual Reproduction 



There are no tetraspores produced in Batrachospermum, but monospores 

 may be developed on the Chantransia filaments. These arise singly in 



Fusion 

 ■ Nucleus 



Oermatium 



Gonimoblast 

 ^Filament Female 



Nucleus 



Carpogonium 

 Carpospore / ^ntheridium 



^Batrachospermum 

 Plant 



Fig. 141. — Life-cycle oi Batrachospermum. 



sporangia borne at the ends of short branches and on liberation give rise to 

 fresh plants of the Chantransia stage. 



Gigartinales 



The Gigartinales are Rhodophyceae in w'hich the thallus is usually divisible 

 into a flat frond and an attaching disc, though in certain parasitic genera the 

 structure of the thallus may be greatly reduced. In the majority the thallus 

 is composed of a tissue of much-branched filaments of cells showing con- 

 siderable morphological differentiation. 



In many species the plants are dioecious, though a few^ are monoecious, 

 but in either case the zygote gives rise to a large tetrasporic plant, morpho- 

 logically like that of the gametophyte. The sexual reproduction involves 

 6a 



