636 RELATION TO ENVIRONMENT. 



phar ad vena), while in some other places the latter is replaced by the white 

 water-lily (Nymphaea odorata). These could be charted as in fig. 535. 



(5) Note the prominent physical characteristics of the soil. 



(6) Note exposure to sun, wind, etc., if so situated as to be especially 

 influenced by these. 



1124. Secondary or subordinate species in a formation. Give special 

 attention to those species which are characteristic of similar physiographic 

 areas. 



(1) Species which occupy similar ground in other districts where they 

 may become dominant species in the formation (example, cranberries occur as 

 scattered individuals in some moors or bogs, while in others they are domi- 

 nant species in the formation, so it is with the cattail-flag in swamps, and 

 with many other plants). 



(2) Species which are characteristic of certain localities but are never 

 abundant enough to dominate the formation (examples: the pitcher plant, 

 sundews, etc., in moors). 



(3) Species which are infiltrated in with the dominant vegetation of a 

 formation and mark this portion off from other patches of the same forma- 

 tion (example, in rolling prairies or grass-land, different flowers on different 

 kinds of soil or where there is a slight variation in soil moisture). 



(4) Guilds (or associates or companions) (examples: Lianas [scramblers, 

 climbers, root-climbers], etc.), epiphytes (examples: Lichens, mosses, etc.). 



(5) Parasites (examples: parasitic fungi on leaves, fruit, flowers, trunks, 

 etc., parasitic flowering plants, as dodder, etc.). 



(6) Wood-destroying fungi. 



(7) Humus-forming fungi, and so on. 



1125. The general features of the study the teacher can illustrate. ist. 

 By lantern slides of photographs of vegetation and formations of different 

 regions not illustrated in the local flora (examples: desert, arctic, alpine, 

 prairie, plains, forests of different kinds, edaphic series of various kinds). 



2d. By photographs illustrating different physiographic areas, or 

 edaphic series, or principal formations, to be studied in the selected locality. 

 These will also show many individual formations in zones or areas. The 

 negatives could be used to make velox prints or blue prints for members 

 of the class to illustrate their study, each student purchasing a set. 



3d. It is desirable, so far as possible, to have at least a small collection 

 of plants especially made to illustrate various features of the study (examples: 

 plants from arctic, alpine, desert, and other regions, especially such as 

 will illustrate such characters as fit them to exist under the peculiar con- 

 ditions, as well as to illustrate plants which are dominant elements of char- 

 acteristic formations). In some cases these can be obtained by purchase 

 or exchange. In addition the teacher can work each year toward making 

 a collection of local plants fo- the purpose of illustrating the various phases 



