1538 



CHAPTER LXVIII. 



SERIES PHANEROGAMS— continued. 



Class Angiosperivle. 



Class II. Angiosperivle. — With this class we come to the highest 

 development of plant life, characterised by the complete enclosure 

 of the ovules and seeds in the ovary, and by the more or less rudi- 

 mental condition of the endosperm. As they are highest in point 

 of development, so these plants are characteristic, as a whole, of the 

 latter periods of the earth's history, so that the Tertiary and recent 

 periods are well described as the " age of Angiosperms." The class 

 may be divided into the two great subclasses of Monocotyledons 

 and Dicotyledons, of which the former is the more generalised, and 

 the first to make its appearance in time. 



Subclass I. Monocotyl^e. — The Monocotyledons are plants 

 having only a single seed-leaf or cotyledon ; and with an endogenous, 

 or inwardly growing stem, in which there are consequently no an- 

 nual rings of growth. It includes the Palms, Grasses, Lilies, &c. ; 

 and it appears that the Palms and Grasses are the earliest known 

 forms ; the perianthed types, or those w T ith large and conspicuous 

 flowers, not making their appearance till a later date. 



There is indeed some doubt as to the earliest appearance of the 

 subclass, but it appears to be certain that most of the Palaeozoic 

 forms which have been described as Monocotyledons are referable 

 to Gymnosperms. There occur, however, certain forms of doubtful 

 affinity in the Upper Palaeozoic, which have been termed "pro- 

 Angiosperms," or types imperfectly developed from a Pteridophytic 

 or Gymnospermic stock, which we may proceed to notice. The 

 best known is the genus Spirangium, ranging from the Carboniferous 

 to the Wealden ; this is based on certain spindle-like bodies, which 

 are believed to consist of from five to ten linear valves enclosing a 

 central cavity, the valves being in some cases spirally twisted. Their 

 affinities are at present totally obscure. From the Russian Permian 



