(29) 



greatly in size and complexity of structure ; but, unlike them, 

 they are devoid of chlorophyl, the characteristic green matter 

 which enables other plants to build up complex food for their 

 nourishment, and consequently they are wholly different in 

 their mode of life. Some are parasitic, deriving their nour- 

 ishment from living plants and causing enormous damage to 

 crops; others are saprophytic, deriving it from the remains 

 of dead organisms ; while others are symbiotic, living in such 

 relationship with chlorophyl-bearing (green) plants that they 

 mutually nourish one another, as in the case of lichens 

 and mycorhizas. There are five generally recognized series 

 here: First we have the stalked-spored fungi (cases 17 to 

 28). This series falls into two groups, the one typified by 

 the " rusts " and " smuts " which are commonly parasitic on 

 the leaves and fruits of other plants; the other the great 

 saprophytic group, well known through the mushrooms, 

 bracket-fungi, stink-horns and puff-balls. Second in the 

 series is the group known as the imperfect fungi (case 29). 

 In this group the spores are borne directly on the threads or 

 " hyphae " which constitute the vegetative portion of the 

 organism. They are often parasitic on the leaves and on 

 the bark of both wild and cultivated plants. Third in this 

 series are the spore-sac fungi (cases 30 and 31). In these 

 plants the spore are borne in delicate membranous sacs, 

 called asci, which in the more complex forms are collected 

 into bodies of various shapes. The plants vary greatly in 

 size and structure and are both parasitic and saprophytic. 

 To this group belong the yeasts and mildews. Some plants 

 grow above the surface of the ground, as in the case of the 

 morel; while others are subterranean, as in the case of 

 truffles. Next in order are the alga-like fungi (case 32) ; 

 these vary in form from simple masses of protoplasm to sim- 

 ple or branching threads. Here belong many of the moulds 

 and similar forms which grow both on other plants and on 

 animals. The fifth and in many respects the most interesting 

 of all the groups is that consisting of the lichens (cases 33 

 to 36). The fungi thus far considered are either parasitic 



