CHAPTER XXII. 



CLASSIFICATION OF PLANTS. 



We have seen in earlier lessons how plants change their forms 

 and habits of growth to suit different conditions of life. Prob- 

 ably none of the familiar plants of the veld look to-day just 

 as they did when they were first created. More than 125,000 

 species or kinds of plants have been described or named, but 

 since differences in soil, the amount of water, or sunlight avail- 

 able and cross fertilization bring about a change in the plants, 

 it is often difficult to say just how many species there are in a 

 district. 



It is impossible to define the term species although it is a 

 word which is in constant use. Species are not fixed by ab- 

 solute characters. For purposes of classification any kind of 

 plant which breeds true, that is, which can reproduce its like 

 (within limits) by seed, which is fairly constant over a con- 

 siderable territory and can be described so that it may be dis- 

 tinguished from other kinds, may be called a species. 



A group of species which are more like each other than 

 they are to olher species is called a Genus, or a genus may 

 comprise but a single species if it has a combination of char- 

 acters not found in any recognized species. 



Just as species are grouped into genera, so genera are 

 grouped into Orders. The many kinds or species of heaths 

 are grouped into the genus Erica. The genus Philippia is 

 similar to Erica, but whereas Erica has three bracts " as a 

 rule," beneath the flower, Philippia has none. If we find an 

 Erica with none we may still distinguish it from Philippia 

 which has a calyx of unequal lobes. Other genera may have 

 but four stamens instead of eight, as found in Erica and 



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