THE BOTANY OF THK FARM. 



flowering plants. In the nutritive and reproductive organs there is no- 

 thing which can be considered of the same value as cellular tissue. 

 In the nutritive organs the embryo occupies the highest place, and by 

 amining it we divide plants into Acotyledonous, having no cotyledons 

 but occasionally producing a cellular expansion (prothallus) ; Monocotyle- 

 donous with one cotyledon; and Dicotyledonous, with two cotyledons. 

 Proceeding to the secondary organs in the nutritive class, we find ill,- 

 stem is Cellular or Thallogenous, Acrogenous, Endogenous, and Exogen- 

 ous. The thallus is veinless, the fronds of Acrogens have often a foi 1 

 ation, the leaves of Endogens are parallel-veined, and those of Exo- 

 i vticulated. In the reproductive system the stamens and pistil< 

 occupy the highest place, as being the essential organs of flowering plants- 

 (Phanerogamia), while peculiar cells (antheridia and archegonia) have the 

 ie value in flowerless plants (Cryptogamia). Succeeding these organ- 

 in value comes the fruit, which is either a theca with spores, or a pericarp 

 with seed. The floral envelopes are the next in the series; they 

 absent in Cryptogamous plants, and present in Phanerogamous ; their ar- 

 .rement is ternary in Monocotyledons, quinary and binary or quaternar\ 

 in Dicotyledons. 



It is impossible to represent the affinities of plants in a linear series. 

 Different groups touch each other at several different points, and 11111^; 



id- red as alliances connected with certain great centres. We find also 



that it is by no means easy to fix the limits of groups. There are cn- 



tly aberrant orders, genera, and species, which form links between the 



groups, and occupy a sort of intermediate position. Hence exact and 



definitions cannot be carried out. 



'I'll.- following is the arrangement of the NATURAL SYSTEM of De Can- 

 , with some division derived from Jussien and Lindley : 



bin iTYLKDONES, EXOGENvE, or ACRAMPHIBRYA, in 



which spiral vessels are present; the .stem is exogeno 

 stomataare present, the venation of the leaves is n-tieiila: 

 the (lowers have stamens and pistils, and the syimijeti\ 

 quinary, binary, or (juaternai y ; the ovules are either in an 

 ovary or naked ; and the embryo is dicotyledonous. In 

 this class there are included four Sub -classes : 

 Sub-cla I. Tn \I.\MII i "i; i . Mowers usually dichlainy- 



denus, petals separate, inserted on the thalaniu 



StaiiM-ns 



