34 Ihtrodtidory View of the Natural Si/stem of PlayitL 



Endogenes, or Mo7iocotyledonous plants, are the first remove 

 from Cellulares, and hold an intermediate rank between them 

 and Eocogenes or Ditotyledonous plants, in which vegetation ac- 

 quires its highest form of developement. They were formerly 

 characterised by having a single cotyledon, but this circum- 

 stance is not only not absolute, but difficult of determination, 

 except after minute analysis. The real difference between their 

 seed and that of Dicotyledones is this, that in Monocotyl^- 

 dones there is only one cotyledon {fig. H.s), or, if two, that 

 they are alternate with each other {figA\.t\ while in Dicotyle- 

 dones they are always opposite, and more than one, sometimes 

 several, as in Pinus. {Jig. 12. 3/.) The physiological structure 

 of the two classes is, however, that by which they are fami- 

 liarly distinguished, and exhibits a beautiful proof of the har- 

 mony that exists between the great features of vegetation and 

 their first principle, the seed from which they originate. In 

 Endogenes or Monocotyledones there is no distinction between 

 wood and bark {Jig. \\.q)\ in Exogenes or Dicotyledones, the 

 wood and bark are distinctly separated, {fig. 12. v.) In Mo- 

 nocotyledones the wood and cellular tissue are mixed together, 

 without any distinct annual layers of the former being evident; 

 in Dicotyledones the wood and cellular tissue have each their 

 particular limits assigned them, a distinct layer of the former 

 being annually deposited. In Monocotyledones there are no 

 radiations from the medulla to the bark ; in Dicotyledones 

 the radiations are distinctly marked. In Monocotyledones 

 there is generally no articulation between the leaves and the 

 stem, while in Dicotyledones the leaves are always jointed 

 with the stem from which they fall off, leaving a scar behind. 

 In Monocotyledones the veins of the leaf pass in parallel lines 



9, Transverse section of a monocotyledonous 

 stem. 



r. Germination of a monocotyledonous seed. 



s. Section of ditto, to show the cotyledon 

 remaining in the testa. 



/, Section of a germinating embryo of a grass. 



to show the two alternate cotyledons of un- 

 equal size ; the back and front lobe represent 

 these, the middle lobe is the plumula 



M, Stem and leaves of a monocotyledonous 

 plant. 



