TH1E CLASSIFICATION OF THE TILOPTEEIDACE^. 185 



Tho group is thus a very limited one, and may be all that 

 survives of a large oogamous group with simple filamentous 

 type of thallus, although more probably it is a recently 

 developed one arising by reduction of megaplanogametes to 

 an ovum, and zoospores to a tetra-nucleate monospore. 



In Tilopteris the oogonia are ordinarily indistinguishable 

 from the sporangia, and now it is no longer safe to assume 

 that, because an individual bears antheridia, the other 

 organs are all oogonia, although in most cases it may be 

 inferred that they are so. In Haplospora globosa (Kjellm.) 

 limit, umtat. the following conditions have been found with 

 regard to the reproductive organs : — 



1. Sporo-hermaphrodite. 



2. Hermaphrodite. 



3. Sporo-antheridic. (Kjellm.) 



4. Sporo-oogonous. 



5. Non-sexual. 



The second and fifth are the typical states, all the others 

 being exceedingly rare. It is extremely likely that all these 

 conditions occur more or less commonly in Tilopteris. Reinke 

 found two, four, or more nuclei in the sporangia of Tilop- 

 teris. and such are probably non-sexual, but the multi- 

 nucleate condition may have been due to the commencement 

 of germination of the spore in situ, which is not uncommon 

 in Tilopteris Mertensii. Certain it is, however, that from 

 antheridia-bearing specimens, uni-nucleate bodies are dis- 

 charged which do not possess a recognisable wall ; hence 

 there can be little doubt that they are ova. 



The process of fertilisation and the subsequent early stages 

 in germination have yet to be observed, but when that is 

 done the life-historj^ of these algse will be practically com- 

 plete, for already most of the germination stages have been 

 observed both in Tilopteris and Haplospora up to the re- 



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