74 PLANTS 



presence of chlorophyll in the former group and its total absence 

 in the latter. Most of them are small, many are microscopic in 

 size, but there are a few marine algae which are extremely large. 



178. The algai are found either in the water or else in moist 

 places, for they have no elaborate protective structures which 

 would prevent desiccation. There are many kinds which con- 

 sist of only a single cell, others of similar cells arranged in rows 

 or filaments. In others, again, the cells are arranged in sheets 

 or masses having more or less definite forms. One group of 

 marine algae in which the structure is rather complex is charac- 

 terized by a reddish color, due to the presence of a red pigment 

 in the protoplasm, which to some extent obscures the green of 

 the chlorophyll. Another group of marine algae, simpler in 

 structure, is similarly characterized by a yellow pigment w^hich 

 gives the plant a brownish color. A small group of extremely 

 simple filamentous or unicellular algae is characterized by a 

 blue-green color due to the presence of a blue pigment. There 

 are many algae, however, which are neither red, brown nor 

 blue-green, but have the yellowish-green color characteristic of 

 chlorophyll. These vary in complexity of structure from the 

 simplest to the most complex. The blue-green and the green 

 algae comprise both marine and fresh water forms. 



179. The fungi vary as greatly in regard to complexity of 

 structure as do the algae and may be regarded as a parallel 

 series, differing chiefly from the algae in those points which are 

 dependent on the presence of chlorophyll. Since they are 

 destitute of chlorophyll, the fungi (excepting perhaps some of 

 the lowest forms) cannot assimilate carbon dioxide and con- 

 sequently are either saprophytic, i. e., nourished upon waste 

 organic matter, or parasite, i. e., nourished upon the tissues of 

 other living organisms. Some of the most familiar of the 

 higher fungi are the toadstools, mushrooms, shelf-fungi, puff- 

 balls, smuts and rusts of grasses, "cedar-apple," ergot, black- 

 knot of plum trees, mildews, molds, yeast, etc. 



