410 



BOTANY OF THE LIVING PLANT 



"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 Siphoneae. They are 

 divided into two sub-cldsses, 

 according to the sexual organs. 

 Where these can be distinguished 

 as ,male (antheridia) and female 

 [oogonid] they are called Oomycetes 

 (Fig. 344). To these belong such 

 parasites as the Peronosporeae, 

 for instance, the Potato Fungus 

 (Phytophthora) ; also the sapro- 

 phytic family of the Saprolegniae, 

 which includes the " Damping-off 

 Fungus " of seedUngs [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 zygospore, as in the common 

 IVIould, Mucor (Fig. 345). These 

 are designated the Zygomycetes, 

 and they are also referable in 

 origin probably to Algae of the 

 The Phycomycetes are dealt with 



Fig. 345. 

 Mucor ynucedo. Different stages in the forma- 

 tion and germination of th^ zygospore. i=two 

 conjugating branches in contact. 2 — septation 

 of the two conjugating cells. 3 = more advanced 

 stage ; the conjugating cells are still distinct 

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

 the suspensors (a). 5 = germinating zygospore 

 with germ-tube bearing a sporangium. {After 

 Brefeld.) (1-4x225: 5 x cifca 60.} (From v. 

 Tavel.) (From Strasburger.) 



type of the living Siphoneae 

 in Chapter XXVII. 



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

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

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

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

 others there are a pair of nuclei, or only one. These septate Fungi are 

 called the Eu-mycetes. The sexual organs of some of them indicate 



