EMBRYOGENESIS IN THE ALGAE 



41 



the illustrations in Fig. 8 show, there is evidence of translocation of 

 nutrients to it. The basal or proximal region, which develops as an 

 organ of attachment, soon becomes more or less highly vacuolated and 

 in general appears to be a region in which the metabolism is consider- 

 ably different from that of the distal region. When a zoospore of 

 Botrydium, Protosiphon or Oedogonium germinates, it elongates and 



*i¥irf 





Fig. 8. Green algae: young plants 



A, B, Protosiphon botryoides. A, Normal plant developed from a zoospore. B, 

 Group of plants, grown from zoospores in a nutrient solution, showing the distal 

 aggregation of dense protoplasmic contents (after Klebs). C, D, Oedogonium 

 concatenatum. Germinating zoospores (after Hirn). E, F, Spirogyra neglecta. 

 Germinating zygospores (after Trondle). 



gives rise to a polarised, ovoid or filamentous structure, in which there 

 is an evident concentration of the protoplasmic materials in the distal 

 region, Fig. 8. This mode of development, which is general in both 

 septate and siphonaceous species, is not unlike the enclosed young 

 embryo in archegoniate and seed plants. Why the distal region should 

 become the seat of protein synthesis is a problem about which little is 

 known. The phenomenon is common to all classes of plants, and it may 

 be that the same, or closely similar, factors determine the characteristic 

 heterogeneous distribution of protoplasmic materials. 



The great majority of green algae might be specified as plants which 

 have never evolved beyond the simple filamentous or embryonic 



