HIDDEN MARRIAGES 



537 



FIG. 681. EARTH STAR (Geaster hygrometricus). 



The outer layers of the peridium have split and curled back, 

 and the spores are escaping from the apical opening. 



Zygomycetes, etc.) they are formed 

 singly or in chains, terminating 

 branches. They may be formed by 

 a division of the protoplasmic con- 

 tents within a mother-cell, which 

 thus becomes a sporange, the spores 

 being liberated by the rupture or 

 disappearance of the sporange-wall. 

 These spores may be motile (zoo- 

 spores) by the activity of cilia, as 

 in Saprolegnia and Peronospora (fig. 

 676), or non-motile, as in Mucor 

 (fig. 678) and the great majority of 

 the Ascomycetes. 



These spores germinate under 

 favourable conditions by pushing 

 out germ-tubes which lengthen and 

 branch until they form a new mycele. Moist and thin-walled spores that 

 do not soon find the conditions favourable to germination perish ; but many 

 dry spores, if kept dry, retain their vitality for very long periods, and some 

 of these (resting-spores) will not germinate until after some definite period 

 from the time they were formed. 

 In some groups there is no sexual 



generation, or at least such has not 



yet been discovered. This is the 



case, among others, of the larger 



Fungi, the Basidiomycetes, which 



includes the Mushrooms. Where 



it occurs it chiefly follows one of 



two methods. In Peronospora, 



Achlya, and possibly some Ure- 



dinese, an oosphere is fertilized by 



the intrusion of an antheridial tube 



from an antherid formed on the 



same or a neighbouring branch. 



In Zygomycetes two special cells 



come together by their apices and 



become firmly united. The apical 



portion of each (gamete) is then cut 



off by a transverse wall, and the 



division between the gametes 



gradually disappears, and the con- 

 tents of both conjugate, the united 



mass growing into a zygosperm. 



Photo by} [* Step- 



FIG. 682. EARTH STAR (Geaster hygrometricus). 



The two outer coats (combined) are shown in the act of 

 splitting into eight segments. . 



