CHAPTER XXIII. 
Some Types of Flowerless Plants.! 
*265. Numerous Classes of Cryptogamous Plants. — While 
there are only two classes of flowering plants (§ 256), and only 
the latter of these need occupy much of the attention of a 
beginner in botany, there are some fifteen classes of flower- 
less plants, so that an elementary book on botany can only 
make the student acquainted with a few specimen groups 
chosen from among these. 
THE STUDY OF PROTOCOCCUS.? 
266. Occurrence. — Protococcus may be found in the water of 
stagnant pools, particularly of those which contain the drainage of 
barn-yards or of manure-heaps. It occurs also in the mud at the bottom 
of eaves-troughs, in barrels containifNg rain-water, or in water standing in 
cavities in logs or the stumps of trees. Water containing Protococcus in 
abundance is greenish (or sometimes reddish) throughout, while examina- 
tion with the naked eye hardly shows the separate particles to which the 
color is due. Portions of the mud on which the plant occurs should be 
carefully scraped off and kept damp for examination, or the water in 
* 1 The author has introduced the study of a few cryptogamous forms thus late in 
the present book more out of deference to general usage than because he thinks it to 
be the best possible order of treatment. He has found it desirable to exhibit (under 
the microscope) and discuss slides of Protococcus, Pleurococcus, Palmella, and so on, 
as soon as the pupil is shown the cellular structure of seeds. This emphasizes and 
makes clear at the outset something of the nature of the vegetable cell. Protococcus 
and Spirogyra may be examined for chlorophyll, and their liberation of oxygen in 
sunlight noted while the work of the leaf is under consideration. Finally the 
structure and the reproduction of all the cryptogamous forms which are to be 
considered at all may be investigated and discussed just before the study of the 
flower is begun. 
*2See Huxley and Martin’s Biology (extended by Howes and Scott) under 
Protococcus. 
