454 BOTANY OF THE LIVING PLANT 



any sexual process been recognised. The fact that in the Hymeno- 

 mycetes generally a fusion of paired nuclei precedes the tetrad-division, 

 and leads to the formation of the spores, indicates that these are of 

 the nature of carpospores. Probably at some stage in the origination 

 of the fruiting body a process leading to a pairing of nuclei will be 

 found. But hitherto it has escaped notice. It seems probable that 

 the fruiting body itself corresponds in the life-cycle to the mass of 

 teleutospores seen in some of the Uredineae. The fact that these 

 may germinate and produce their carpospores in situ gives probability 

 to this comparison. 



Basidio-Lichens. 



Certain Basidiomycetous Fungi take part in the composition of 

 Lichens, but this is much less frequent than in the Ascomycetes. 

 The most familiar example is the genus Cora, found not uncommonly 

 in the tropics, growing on the ground or on trees. Its form is not 

 unhke a Stereum, or Thelephora ; and, like them, its hymenium is 

 on the lower surface. The fact that the fungal constituent of some 

 Lichens can be referred to Basidiomycetous Fungi may be held as 

 a final proof of their being coahtion-organisms (see pp. 438-440). 



Fungi as Subaerial Plants. 



The Fungi, sprung probably from various Algal sources, show some 

 degree of adjustment to subaerial life parallel to that already seen in 

 Green Plants. But as the hypha is the basis of their construction, 

 their vegetative system gives less opportunity for adaptive change 

 than their propagative organs. 



The most striking modifications are seen in the Phycomycetes, 

 which are referred in origin to non-septate Algae having motile zoo- 

 spores and gametes. Among the Oosporeae the aquatic origin is clearly 

 reflected in the germination of the conidia, where each bursts and 

 gives rise to zoospores motile in water (Figs. 351, 355, pp. 415, 420). 

 The conidium here appears in fact to be a sporangium hke that seen 

 in many Algae, but reduced in size and detachable, so as to secure 

 the spread of the organism through air, though its germination is still 

 carried out in water. Similarly in the Zygosporeae the large spor- 

 angium of Mucor is also effective for water-distribution of its spores, 

 though they are not themselves motile (Fig. 360, p. 425). But within 

 the family of the Mucorini the sporangium is liable to be reduced in 

 size, with increase in its numbers, till in Chaetocladium and Pipto- 



