208 The Natural System of Botany. 



three valves. The essential characters of Violaceae are th 

 a persistent calyx, irregular flower, anthers with a membrano ' 

 crest, and a three-valved fruit, with a parietal placenta in th 

 middle of each valve. 



The order is not a large one, but contains several useful and 

 ornamental species, some of which are among the most com 

 mon favorites of the garden. The roots of nearly all the orde 

 possess emetic properties, and the Ipecac, so generally used in 

 medicine, is produced by a South American species. For th 

 genus Viola, the reader is referred to the last number of this 

 work, where he will find more particular mention made of its 

 species. 



Order — Droserace.*:. The Sun-dew Tribe. 



This is a small order, containing some very curious plants, 

 They are all small and delicate, and are distributed in wet 

 places over a great portion of the world. Two or three species 

 of Drosera, from which genus the order takes its name, are 

 found in the Northern States. A description of the most com- 

 mon species, Drosera rotundifolia, will show what singular 

 characters belong to these plants. This Sun-dew may be 

 found in bogs, on those roundish tufts which are surrounded by 

 water, and on the muddy shores of ponds and rivers. It is a 

 litde plant, not more than four or five inches high. The leaves 

 are nearly round, on long hairy stalks, lying flat on the ground. 

 At first they are rolled up, but when spread out and full 

 grown, they form a concave disk, covered with long, red, 

 shining hairs, on the point of each of which is a drop of clear, 

 clammy fluid, which appears like dew glistening in the sun. 

 That it is not real dew is readily ascertained ; since it is most 

 conspicuous at mid-day, when the dew is entirely dried up. 

 These hairs, when placed under the microscope, are found to 

 consist of a great number of parallel cells, and to be most 

 beautifully variegated with pink, green, and yellow. Each 

 hair is tipped with a most brilliant red point, from which 

 exudes the fluid, which is acrid to the taste. The hairs, when 

 an insect alights on them, curve inwards so as to retain it. 

 The flowers are very small, white, arranged on one side of the 



