SYNGENESIA. 



set, or tube. In addition to the number and union of the sl.a 

 metis, this class is characterized by the flowers being com- 

 pound, that is, many individual small flowers, or florets, as they 

 are called, are clustered together on a common receptacle, 

 forming heads, as in the Daisy, Dandelion, and Thistle 

 These clusters, or heads, are surrounded by a common calyx, 

 or more properly, an involucrum. 



This is one of the best denned and most extensive of all 

 the Linnaean classes. Its importance to man, is not, how 

 ever, in proportion to the number of its genera, though it con 

 tains many culinary and medicinal plants, and a large nurnbei 

 of very popular ornamental species. 



The inflorescence of the Syngenesious tribe differs so en 

 tirely from the classes heretofore described, that it becomes 

 necessary to explain more particularly than we have done, 

 the analogy between the various parts of these flowers, and 

 those which the student is supposed to have already exam- 

 ined, and also to define the words used in describing them. 



The capitum, or head, is a cluster of florets inserted on a 

 common receptacle. Ex. Thistle, Dandelion. 



Involucrum, is the calyx, or lower and most external part 

 of the head, and is composed of a greater or less number 

 of green, or colored leaves, in the form of scales, either 

 placed in a single circular row, or in several rows, one above 

 the other. When these scales are in a single row, arid united 

 by their edges, the calyx is called one-leaved, or monophyl- 

 lous, when in several rows, one above the other; it is called 

 imbricated. If the external scales surround the internal at 

 the base, the involucrum is said to be calyculated, or caly- 

 culate. 



The receptacle is the upper termination of the stem, or stipe, 

 enlarged, and surrounded by the involucrum. On the ex- 

 panded surface of the receptacle sit the florets, crowded 

 thickly together, and forming the head. 



Each floret consists of a tube or corolla, and a germen, 

 which, when ripe, forms the seed. 



What does the term Syngenesia signify ? How many stamens have 

 the flowers of this class ? Are the anthers distinct or not ? What other 

 distinctive characters has this class besides those just mentioned ? What 

 is said of the extent of this class ? What is the capitum or head of a 

 compound flower 1 What is the involucrum of a compound flower 1 When 

 is the calyx monophyllous ? When is the calyx imbricated, and when 

 calyculate ? What is the receptacle of a compound flower ? 



