SECT. I. ORGANOGRAPHY AND GLOSSOLOGY. 



115 



of the coniferous tribes (the fir trees), which possess 

 several cotyledons. 



An attempt has been made, to establish an affinity 

 between the embryonic structure of dicotyledons and 

 monocotyledons, by supposing the single cotyledon in 

 the latter class, which completely envelopes the 

 rest of the embryo, to be in reality compounded 

 of two cotyledons, united by their edges into one 

 mass. In some cases this occurs in dicotyle- 

 dons; and the annexed figure (128.) represents 

 a monstrosity, observed in a young plant of 

 the sycamore, which exhibits an approximation 

 to the condition of a monocotyledon, at the 

 commencement of its germination : the two 

 cotyledons having adhered by one of their 

 edges nearly throughout their whole lengths. 



In all monocotyledons, it is more difficult to determine 

 the several parts of which the embryo is composed, than 

 in dicotyledons. It generally consists of a nearly cylin- 

 drical fleshy mass, without any external traces of organis- 

 ation ; but if it be cut longitudinally, the position of the 

 radicle and the gemmule may then be seen, traced by a 

 faint outline, indicative of a separation in the substance 

 of the embryo (fig. 25.). 



(113.) Reproductive Organs 

 of Cryptogamic Plants. The 

 sporules mentioned in art. 36. 

 are contained in pecu liar cells 

 placed on the surface, or em- 

 bedded in the substance of 

 the plant, among the crypto- 

 gamic tribes. Among the higher families O t tais class, 

 the cells assume a distinct capsular form, 

 termed "theca" (fig. 12y.), which has 

 various characters, in the ferns (a), Equi- 

 seta (6), mosses (c), &c. The cells, 

 or cases which contain the sporules, among 

 the inferior families of this class, are more 

 simple in their structure, and often re- 

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