THALLOPHYTA. 



;7i 



in the oogonia (fig. 382), and these germinate parthenogenetically. Although the 

 sexual organs are still preserved in this group their function has been lost, leading 

 the way to their complete atrophy in many other groups of Fungi. Many members 

 of the group occur upon the bodies of dead insects and fish {e.g. various species of 

 Saprolegnia, Achlya, Aphanoinyces). Aphanomyces plcycophilus is parasitic upon 

 Algce (e.g. 8'pirogyra) and Saprolegnia 

 Ferax upon Salmon, &c. 



About 45 species have been distinguished. 



Cltytridiacew. — Small parasitic aquatic 

 Fungi whose mycelium is almost entirely 

 wanting; they produce characteristic spor- 

 angia which liberate uniciliate swarm-spores. 

 PolypJtagus EuglencG develops a very delicate 

 mycelium, of which the branches become 

 attached to Euglena-cells (fig. 379 ^ two 

 Euglenas are thus attacked), and from the 

 central portion of the mycelium arises a 

 sporangium from which uniciliate swarm- 

 spores (fig. 379 ^) are liberated. These in 

 turn germinate, develop threads, and entangle 

 fresh Euglenas. Rhizidiomyces attacks the 

 oogonia of Saprolegnias, sending a branching 

 mycelium into their interior (fig. 379^) and 

 producing a pear-shaped sporangium at the 

 surface which liberates numerous swarm- 

 spores. Chytridium Olla (fig. 380^) pro- 

 duces its sporangia on the oogonia of (Edo- 

 goniuni; its swarm-spores escape by the 

 removal of a lid. 



Over 180 species are known. 



Ancylistacece. — Very nearly resemble the 

 Chytridiaceae in mode of life, but difier in 

 exhibiting sexuality. Lagenidium Rahen- 



horstii attacks cells of Spirogyra, &c. The spores become attached to the Sjnro- 



I gyra-ceWs, and penetrate the wall (fig. 379 1) by means of a tube which branches 



about within, forming a lobed, irregular body (fig. 379 -), which may open at the 



I outside, liberating swarm-spores (fig. 379 ^), or sexual organs may arise inside and 



j fertilization take place. 



14 species have been distinguished. 



Entomophthoreoi.—k group of forms almost all of them parasitic on insects. 

 They are adapted to non-aquatic life, and connect the Peronosporere with the 

 Zygomycetes. 



The tubes of these parasites having eflfected an entrance into the body of an 



Fig. Z?,1.—Achhja liijnicnla. 



Oopoiiia with antlieridia and feitiliziiis tubes; no fer- 

 tilization liapijeiis, however. 2 An oogonium coii- 

 taiuiug egg-cells which have put ou cell-walls with- 

 out being fertilized. » and 2 x 400. (After Sachs.) 



