288 BIOLOGY. 



development, which range parallel to the vegetable 

 , classes ; since it is impossible for any other organs to 

 \ originate in them but such as belong to the idea of the 

 ) plant. The lowest fungus can therefore change only, by 



endeavouring to develop in itself ducts, tracheae, roots, and 



such like parts. 



1537. There are accordingly as many developmental 

 stages of the fungi as there are vegetable classes. These 

 divisions are called families. 



1538. The vegetable families range parallel to the 

 classes. This law must hold good of all the classes. 

 There are therefore in each class 16 families. An associ- 

 ation of families upon each stage may be called an order. 



1539. At first the fungus is none other than a mucus- 

 vesicle or a small cluster of vesicles, e. g. an uredo or 

 mildew. Such a vesicle next becomes longitudinally 

 extended, and includes within itself other vesicles or 

 granules, e. g. mould. These mould-filaments or threads 

 unite again so as to form a common mass, which is sur- 

 rounded by an external membrane, and is then called 

 puff-ball. The pulverulent granules, which were irre- 

 gularly accumulated in the puff-balls, unite at length 

 in a regular manner to constitute a trunk of varied form, 

 as in the ascomycetes, e. g. spharia. Finally, the mould- 

 filaments with their sporules are regularly collected toge- 

 ther in an investing membrane, which, like a puff-ball, 

 is supported upon a stipes or stem, e. g. the sarco- 

 mycetes or agarics. There are therefore 5 develop- 

 mental stages of the fungi, which correspond to those 

 of the classes ; viz. the parenchyma, shaft, stem, flower, 

 and fruit ; and constitute orders. 



1540. Each order is resolvable again into three divi- 

 sions or families, which correspond to the organs. Thus 

 there are in each class 16 tribes or families, which ob- 

 viously range parallel to the vegetable organs or classes. 

 (Vid. Tab. B.) 



1541. A tribe or family is consequently the repre- 

 sentation of a vegetable organ within a class. 



1542. The genera obey the same law; for essential 



