CHAPTER XXVII 



STUDIES IN CRYPTOGAMS 



The special advanced pupil who has acquired skill in 

 the use of the compound microscope may desire to make 

 more extended excursions into the cryptogamous orders. 

 The following plants, selected as examples in various groups, 

 will serve as a beginning. 



AIXLE 



The algae comprise most of the green floating "scum" which covers 

 the surface of ponds and other quiet waters. The masses of plants 

 are often called "frog spittle." Others are attached to stones, pieces 

 of wood and other objects submerged in streams and lakes, and many- 

 are found on moist ground and on dripping rocks. Aside 

 from these, all the plants commonly known as seaweeds 

 belong to this category. They are inhabitants of salt water. 



The simplest forms of alga; consist of a single spherical 

 cell, which multiplies by repeated division or fission. 

 Specimens of these may be found growing on damp rock 

 and the shady side of trees. Most of the forms found in 

 fresh water are filamentous, i.e., the plant-body consists 

 of long threads, either simple or branched. Such a plant- 

 body is termed a thnlhis. This term applies to the vege- 

 tative body of all plants which are not differentiated into 

 stem and leaves. Such plants are known as thallophytes 

 (353). All alga? contain chlorophyll, and are able to as- 

 similate carbon dioxid from the air. This distinguishes 

 them from the fungi. 



Spirogyra. — One of the most common forms of the 

 green algse is spirogyra. (Fig. 340.) This plant frequently 

 forms the greater part of the floating green mass on ponds. 

 The filamentous character of the thallus can be seen with 

 the naked eye or with a hand lens, but to study it carefully 



^a 



340. Strund of 

 spirogyra, 

 showing 

 the chloro- 

 phyll bands. 

 There is a 

 nucleus at o. 



a microscope magnifying two 



hundred 



ri85) 



diameters or more should 



