FUNGI. INTRODUCTORY 



399 



is not yet fully known, often because one stage is commoner, or more 

 obvious than another. Those Fungi in which the knowledge of the 

 life-cycle is incomplete are called "Fungi Imperfecti , \ and they 

 constitute a large proportion of the described species. 



It will be gathered from the preceding pages that the Fungi provide 

 characters, vegetative, propagative, and also functional, which will 

 serve for their classification, though 

 the data may often be insufficient 

 for a final decision. Those Fungi 

 which have non- septate hyphae 

 are called Phycomycetes. Their 

 structure is relatively coarse, and 

 corresponds in this, as well as in 

 the absence of septa, to what is 

 seen in the Siphonales. They are 

 divided into two sub-classes, 

 according to the sexual organs. 

 Where these can be distinguished 

 as male (antheridia) and female 

 (oogonia) they are called Oomy- 

 cetes (Fig. 296). To these belong 

 such parasites as the Perono- 

 sporeae, for instance, the Potato 

 Fungus (Phytophthora) ; also the 

 saprophytic family of the Sapro- 

 legniae, which includes the 

 " Damping-off Fungus " of seed- 

 lings (Pythium). The latter live 

 on vegetable or animal matter 

 decaying in water. In the second 

 sub-class there is conjugation of 

 similar bodies to form a zygo- 



Fig. 297. 

 Mucor Mucedo. Different stages in the forma- 

 tion and germination of the zygospore, i = two 

 conjugating branches in contact. 2 = septa tion 

 of the two conjugating cells. 3 =more advanced 

 stage • the conjugating cells are still distinct 

 from one another. 4 =ripe zygospore (b) between 

 5 = germinating zygospore 



the suspensors (a). 



with germ- tube bearing a sporangium. (After 

 Spore, as in the Common MOUld, Brefeld.) (1-4x225, 5 x circa 60.) (From 

 ,„. N ^p, 1 Strasburger.) 



Mucor (Fig. 297). These are de- 

 signated the Zygomycetes and have been referred in origin to Algae 

 of the type of the living Siphonales. The Phycomycetes are dealt 

 with in Chapter XXV. 



The great bulk of the Fungi are probably distinct in Descent from 



these. The structural distinction lies in their septate hyphae. The 



constituent 4: cells " between the septa vary in length and in nuclear 



condition. In some cases the nuclei are small and numerous : in 



b.b. 2 c 



