FUNGI. INTRODUCTORY 



409 



spores. It suggests also the other side of the question, the vast 

 number of germs that never find the suitable nidus. 



Like other Thallophyta, Fungi may bear organs of sex, which lead 

 up to the production of certain types of spore [carpospores). They 

 thus show a life-cycle with successive stages comparable with that 

 of autophytic plants. But in many of those which are regarded 

 as the most advanced, and especially in the larger Agarics, sexual 

 propagation is not normally carried out, and the organs of sex may 

 be actually absent. Various stages of functional perversion, and of 

 atrophy of the sexual organs, are illustrated by less advanced Fungi. 

 Most Fungi have thus two forms of spores in their life-history, conidia 



Fig. 344. 



Development and fertilization of the ovum of Pyihium. The granular protoplasm 

 of the oogonium [c) collects into a ball, and the antheridimn sends in a fertilising 

 tube. In [h] and (c) transmission of contents into the ovum is sho^^m. [d) The 

 ovum has formed a cell-wall, and lies loosely in the oogonium. Highly magnihed. 

 (After Marshall Ward.) 



and carpospores : some of them have more than two. These being 

 borne on distinctive bodies, such as conidiophores or spore-fruits, 

 differ in appearance, though they are really stages in one life-story. 

 Sometimes in parasitic Fungi these stages may appear on different 

 hosts, as in the Rust of Wheat, where the one stage is on the Wheat 

 another on the Barberry (p. 442). Naturally, before the facts were fully 

 known, such stages were liable to be regarded as different Fungi, and 

 described by distinct names. For instance, the Rust on Wheat 

 was called Puccinia, while the stage on the Barberry was described 

 as Aecidium. Later these were proved to be merely parts of the 

 same life-history, and they were given a single designation. But 

 in many Fungi the life-history is not yet fully known, often because 

 one stage is commoner, or more obvious than another. Those Fungi 

 in which the knowledge of the life-cycle is incomplete are called 



