36 TALKS AFIELD. 



alous. When all the sepals, all the petals, 

 all the stamens, and all the pistils are alike, 

 the flower is regular ; when any or all of 

 them are unlike, as in the pea and bean, or 

 when a gamopetalous corolla is not equally 

 lobed, as in the mint, it is irregular. 



In this connection it remains but to be 

 said that flowers vary as widely in size and 

 in appearance as they do in essential struc- 

 ture. The smallest of flowers is that of the 

 little Wolffia which floats on ponds through- 

 out most of the Northern States, the entire 

 plant being smaller than an ordinary pin- 

 head. The largest flower is that of the Raf- 

 flesia, a parasitic plant of the Javan forests. 

 They are sometimes over a yard across. 

 Many flowers possess no colors other than 

 green. The flowers of our grasses and ce- 

 real grains are green and usually inconspic- 

 uous, and the same may be said of the flow- 

 ers of most forest trees. 



The manner in which the stems of flower- 

 ing plants increase in diameter must next 

 demand our attention. There are two gen- 

 eral methods by which this increase takes 

 place. If we cut off a corn-stalk (Fig. 43) 

 we observe that there are many threads run- 

 ning through it lengthwise. A cross-section 



