172 THE CLASSES POLYGAMlA AST) CEYPTOGAMIA. 



Hydrocharis in Enneandria. Coniferous trees monopolize the last order, Monodel- 

 phia viz., Juniperus or Juniper, and Taxus, or Yew. 



Fig. 378. Dicecia Decandria. Fig. 379. Dioecia Polyandria. Fig. 380. Dicecia Monodelphia. 



The Salix and the Populus are capable of yielding a medicinal substance, which is 

 said to be a good substitute for Quinine ; the Juniperus an oil which is employed both 

 medicinally and in the preparation of Hollands ; and the Humulus a bitter principle, 

 which should be used in the manufacture of ale, and a narcotic principle which is 

 employed in medicine. The Taxus is one of our most enduring trees, and has been 

 known to live upwards of two thousand years. The latter plant offers glandular woody 

 tissue, with a spiral fibre (Fig. 60). The Mistletoe Berry, Viscum Album, is an essential 

 element in our Christmas arrangements, and has been so for many ages. The plant is 

 one of those which took part in the ancient Druidical rites. The whole class possesses 

 acrid or narcotic acid poisonous properties. 



CLASS XXIII. POLYGAMIA. 



This represents a condition of the sexual organs which is intermediate between the 

 two last classes ; and has hermaphrodite or unisexual flowers indifferently on the same 

 or on different plants of the same species. It has but one member the Atriplex, a 

 common and valueless weed on dunghills and waste places. It has seven species. 



CLASS XXIV. CRYPTOGAMIA. 



The characteristic peculiarity of the members of this class is, that they do not possess 

 sexual organs, or that they so conceal them that they have not as yet been discovered. 

 But very few, comparatively, were known to Linnaeus ; and of those known in our day, 

 the most beautiful, as well as the greatest numbers, are foreign to our shores. Some 

 of them inhabit the most desolate regions, as the Lichens of Lapland ; whilst others 

 abound in tropical regions, as the Tree-ferns, to which reference has already been made. 

 They are commonly known as Sea-weeds, Mushrooms, Lichens, Mosses, and Ferns, all 

 of which are flowerless Sea- weeds. 



The term Algae is a comprehensive term, capable of wider signification than the 

 corresponding one of Sea- weeds, by which it is commonly represented in our language. 

 It comprehends a very large proportion of the lowest division of the vegetable kingdom, 

 or that which seems to be almost common ground between the lowest forms of both 

 vegetable and animal organization. It is now commonly divided into several groups, 

 as the Brittle-worts, Confervas, true Sea- weeds, Eosetangles, and Charas. 



Brittle-worts (Diatomaceae and Desmidiae) constitute the slime which is found upon 

 the surface of stems, and are commonly so minute as to be microscopic objects. They 

 are fragmentary, brittle bodies, generally bounded by right lines, and of a green colour ; 

 and with the slime in which they nestle afford protection and food to microscopic ani- 

 malcules. Many of them inhabit salt, and others the fresh waters, and most of them 

 develop starch within their cells. Amongst the chief genera we may mention Diatonia, 



