98 ELEMENTARY BOTANY. 



attached to their host-plant during the winter. In the spring 

 they germinate by sending out from each cell a jointed fila- 

 ment, called the pramycelium. On small branches of the pro- 

 mycelium, small terminal cells, or sporidia are formed. These 

 are carried about by the wind, some of which may alight on 

 the proper host-plant. Here germinating, they send their fila- 

 ments into the parenchyma of the leaf, from which a myce- 

 lium proceeds that gives rise to an secidium, and so on, as 

 before described. In some species all the stages may grow 

 on the same plant; more often the secidial stage is found on 

 one plant and the other stages on some other one ; or, in yet 

 other species, each stage may have a different host-plant. The 

 Wheat Rusts belong to the second group; the secidial stage 

 of one of the species occurs only on the Barberry leaves and 

 the uredospores and teleutospores are found on Wheat and 

 other Graminese. 



Collect Mushroomg, Toadstools, PufF-balls, Pore-fungi (Polypori), Black- 

 knot, etc. and draw figures to illustrate all that can be seen without the aid 

 of the microscope. Those species which are usually called "microscopic 

 fungi," many of which are parasitic on leaves and other parts of common 

 plants, as Leaf Mildew, Smut, Eust, "Leaf-spot," etc., can scarcely be 

 studied to advantage by the beginner, but the important ones should be 

 recognized as such at sight. Therefore as many as possible should be col- 

 lected and compared, examined under the lens and notes and drawings made. 

 They can best be preserved (after drying under pressure) by enclosing in 

 paper pockets glued to the herbarium sheets. 



13. The Lichens constitute a peculiar and very interesting 

 group of plants. They are found on tree trunks, old rails, 

 etc., also occasionally on the ground. They have generally a 

 greenish -gray color, but are in some cases yellow or of other 

 colors. They are rather small plants, usually flatfish, but in 

 some cases branching. The tissue of the Lichens consists of 

 jointed, branching, colorless filaments similar to the hyphse 

 of the Fungi. These are attached to or surround small green 

 bodies called gonidia, which are now known to be imprisoned 

 Algffi. The latter furnish food for the Lichens and are pro- 

 tected by them in return for this service. Such a mode of 



