SYSTEMATIC BOTANY. 95 



Collect representative Algae from running water where the coarse branch- 

 ing kinds abundantly occur. The fine silky sorts will mostly be found in 

 stagnant water. On the wet ground or often on flower-pots in the green- 

 house, the kinds that form a felted mass can be found. The individuals of 

 only the coarser kinds can be clearly seen with a pocket lens. If desired to 

 make herbarium specimens, float a quantity in a basin of water ; insert under 

 the mass a piece of writing-paper. Slowly lift the paper, at the same time 

 spread the Algse evenly over it with a small camel' s-hair brush. After the 

 surplus water has drained off, put the paper with the Algae on it under pres- 

 sure between blotting-papers, first having laid a piece of muslin over the 

 Algae. The latter will adhere to the paper but not to the cloth. 



12. The Fungi include a large number of cryptogamous 

 plants of varied size and character ; some are large and complex 

 in structure, others are microscopic and simple. They are desti- 

 tute of chlorophyll, and either live on decaying matter (sapro- 

 phytic), as Mushrooms, Toadstools, Puff-balls and Moulds, or 

 inhabit and draw their nourishment from living plants, as the 

 Rusts, Smuts, Leaf-Mildews, Black-knot, Ergot, etc. These 

 (the parasitic species) cause many of the so-called diseases of 

 plants. Their vegetative portion, or mycelium, consists of 

 delicate tubular threads (called hyphse) that penetrate the 

 tissue of the host-plant and absorb nourishment that the host 

 provided for its own use. Some of them, for example the 

 family Uredinese (Red and Black Rusts) are polymorphic; 

 that is, in their life-course they take on at successive periods 

 two or more distinct forms, so unlike each other generally 

 that the different stages were formerly considered as distinct 

 plants. The mycelium penetrates between the cells in the 

 tissue of leaves, sometimes causing abnormal growth or dis- 

 tortion. There then appear, beneath the epidermis, globular 

 masses, having within at their base a compact layer of upright 

 hyphse, each of which produces a chain of conidial spores. The 

 epidermis is ruptured by the growing mass ; and the thin 

 layer of cells, or peridium, enclosing the spores breaks open ; 

 the yellow spores, hitherto many-sided from mutual pressure, 

 become round and escape. This stage formerly received the 

 generic name of JScidium (Fig. 121). The spores may, there- 

 fore, be called the eecidiospores. There are often present also 



