THE FUNGI 229 



less usual ; the majority are of saprophytic habit, and to 

 this group many of the commonest " moulds " belong. 



We have chosen as our type a little Fungus which is 

 often found growing on old manure-heaps. In spite of 

 its disagreeable habitat, Pilobolus, and especially the species 

 P. crystallinus, is a decidedly pretty object. The part of 

 the plant which alone rises above the surface of the 

 substratum and so meets the eye, consists of the stalks 

 bearing the asexual sporangia. Each of these stalks is 

 about a quarter of an inch high, and swells up near the 

 top into a neat little crystalline globule, surmounted by 

 a kind of black cap, which is the sporangium itself 

 (see Fig. 96, A). These facts will enable us to recognise 

 the plant. We will now consider its structure more in 

 detail. 



1. STRUCTURE 



The mycelium or vegetative thallus of Pilobolus and 

 its allies is made up of repeatedly branched hyphae, 

 which spread in all directions through the substratum. 

 Histologically these hyphae have the same structure as in 

 the Oomycetes ; they are without transverse walls, at 

 least in the vegetative condition, and their protoplasm 

 contains very numerous small nuclei, the whole plant 

 being a non-cellular but multinucleate organism. Thus 

 this order betrays unmistakable affinity to Algae of the 

 Vaucheria type, and therefore Oomycetes and Zygomy- 

 cetes are grouped together in one class, under the name 

 of Phycomycetes or algal Fungi. The group to which 

 Pilobolus belongs has, however, departed much further 

 from the algal stock than the Oomycetes have, for the 

 plants are thoroughly adapted to a terrestrial mode of 

 life, and the power of forming zoospores is altogether lost. 



