EU-MYCETES. (b) BASIDIOMYCETES 455 



cephalis it matures as a single detachable cell. In fact it is an air- 

 borne conidium, their large numbers being a set off against the uni- 

 cellular condition of each. The Oosporeae and Zygosporeae thus 

 suggest a parallel progression from sporangia producing numerous 

 germs to small wind-borne bodies, ranking as conidia. The profuse 

 propagation of the Eu-mycetes by various' types of detachable uni- 

 cellular spores, also called conidia, acts biologically in the same way, 

 as a means of sub-aerial propagation and distribution. But the 

 phyletic origin of such spores was probably from a source distinct 

 from that of the Phycomycetes. 



On the other hand, the sexual organs in Pythium and Cystopus 

 correspond in form and general characters to those of the Siphoneae, 

 such as Vaucheria. But in place of a dehiscent antheridium, shedding 

 spermatozoids motile in water, a fertilising tube is found, which, 

 like a pollen-tube, transfers its contents directly to the ovum 

 (Fig. 357, p. 422). It is in fact an antheridium, which being sub-aerial 

 in its development does not dehisce to set free motile gametes. In 

 the Mucorini the zygospores may very probably be regarded in the 

 same way, but referable to a more primitive state of sexuality. Two 

 distal gametangia, instead of dehiscing and their separate gametes 

 fusing, conjugate as a whole, producing the coenocytic zygospore (Fig. 

 345, p. 410). This may be held as a sub-aerial modification of the 

 conjugation of gametes of the type seen in Bryopsis. Such examples 

 do not provide so coherent a series as the green Plants do. But they 

 accord with the general reference of Land-living Plants in their origin 

 to an aquatic ancestry ; and they illustrate how the modifications 

 in Thallophytes may run parallel with those of organisms higher in 

 the scale. Such parallels go far to support the general thesis that 

 Plant-Life originated in the water, and spread later to land-surfaces. 



