CHAPTER VII. THE THALLOPHYTA. 



3°9 



six orders, as follows : The Chytridiea, the Ustilaginea, the Phy- 

 comycetes, the Ascomycetes, the ALcidiomycctes or Urcdniece, and the 

 Basidiomycetes. 



The Chytridie^e. 



This order, as we have seen, are Fungi of the simplest organiz- 

 ation, most of them being unicellular, and not producing hyphae, 

 while a few of the higher forms produce rudimentary hyphae. 

 They reproduce asexually by means of uniciliated swarm-spores. 

 Sexual reproduction has been observed in but one species, and 

 in this instance it takes place by conjugation. In the typical 



genus Chytridium, the plants 

 are unicellular, and their hab- 

 itat is the interior of the living 

 or dead tissues of aquatic Fungi 

 and Algae. The cells, on reach- 

 ing maturity, become sporangia 

 and emit swarm-spores, which 

 again germinate in the same 

 plant, or, escaping, find 

 their way to others and 



there germinate. 

 Fig. 508. 



See 



ric 508. — Chytridium Olla. A, oogonium of CEdogonium rivulare, with an immature 

 oospore killed by the parasite : the oospore contains several resting-spores of Chytridium, 

 which ripened in October ; three of these spores are still unchanged : two have germinated. 

 By turning the specimen round, it was seen distinctly that the empty sporangium a, was 

 formed from the resting-spore a', and the sporangium b, which is ejecting its contents,from 

 ^';near the mouth of 6, are the cast-off lid and two zoospores. Magnified 600 diameters. 

 Figure and description after De Bary. 



The UstilaginEjE. 



The Ustilagineae or Smut-Fungi, of which the common Corn- 

 sniut, Ustilago Maidis, may be taken as the type, are parasitic 

 upon flowering-plants. The slender mycelial threads usually 

 penetrate through the intercellular spaces of the host-plant, and 

 in some species send sucker-like branches, called haustoria, into 

 its cells. In some instances the parasite attacks the seedling 

 plant and sends its hyphae through the whole structure, growing as 

 it grows ; in others it attacks the more mature plant, and confines 

 its ravages to certain parts. 



At maturity it produces, either at the outside of the host-plant, 

 or in its inter-cellular spaces, very numerous spores on tangled 



