889 



dividuals of these primary groups are distinguished in all parts of 

 their structure. 



ROOT. STEM. LEAVES. PRTS. OF FLOWER. SEED. 



Endoihizous. Endogenous. Reticulate. Ternary. Monocotyled. 



Exorhizous. Exogenous. Parallel Veins. Quaternary or Dicotyledonous. 



Quinary. 



Heterorhizous. Acrogenous. Forked Veins. Absent. Acotyledonous. 



Here tlie Monocotyledons are Endorhizous, Endogenous, with 

 parallel-veined leaves, and a ternary division of the flowers ; while 

 the Dicotyledons are Exorhizous, Exogenous, with reticulate-veined 

 leaves, and a quaternary or quinary division, of the flower. Here is a 

 set of characters which will clearly distinguish a Monocotyledonous 

 from a Dicotyledonous plant, although some one or other of the cha- 

 racters may be departed from in a particular instance. Moreover, 

 Mr, Edmonston forgets that the definition of the Dicotyledonous 

 group includes those plants that have two or more opposite cotyle- 

 dons ; while that of Monocotyledons admits plants with two cotyle-- 

 dons, if they are alternate. Lindley, in his definition of Dicotyledons 

 says, " Embryo with two or more opposite cotyledons ; " and in that 

 of Endogense or Monocotyledons, " Embryo with but one cotyledon, 

 or if with two, then the accessory one impei'fect and alternate with 

 the other." After this explanation, the objection to the terms Mono- 

 and Dicotyledons becomes a mere verbal quibble. 



What is said above will also answer another objection of Mr. Ed- 

 monston's, " that the structure of the seed is too much used in the 

 definitions of the natural school," and " that the characters of the pri- 

 mary divisions ought always, if practicable, to be taken from parts 

 easily seen, or at least not requiring such delicate microscopical in- 

 vestigation as the natural system requires ; " for if he finds a plant 

 whose germination is exorhizous, whose stem is exogenous, whose 

 leaves have reticulated veins, and whose floral organs are quaternary 

 or quinary, he may be sure that it is a dicotyledon without an exami- 

 nation of the seed ; nay, if he only observe that the stem is exoge- 

 nous, the leaves reticulated and the parts of the flower quaternary or 

 quinary, he will never be mistaken as to the group to which he ought 

 to refer it ; and these parts are, I imagine, sufficiently obvious. 



But the examination of the structure of the seeds of plants is more- 

 over absolutely necessary in any system where the affinities of plants 

 are taken into account. Linnaeus used the parts of the flower as the 

 basis of his artificial system, as being the least variable of the parts of 

 plants ; and it must be allowed that the structure of the seed is^even 



