PREFACE. ix 



is overcome. But it is hardly necessary to say, that in natural 

 histoiy many facts which have been originally discovered by 

 minute and laborious research, are subsequently ascertained to be 

 connected with other facts of a more obvious nature ; and of this 

 Botany offers perhaps the most striking proof that can be adduced. 

 One of the first questions to be determined by a student of Botany, 

 who wishes to inform himself of the name, affinities, and uses 

 of a plant, seems to be, whether it contains spiral vessels or not, 

 because some of the great di\dsions of the vegetable kingdom are 

 characterised by the presence or absence of those minute organs. 

 It is true that careful observation, and multiplied microscopical 

 analyses, have taught Botanists that certain plants have spiral 

 vessels, and others have none; but it is not true, that in practice so 

 minute and difficult an inquiry needs to be instituted, because it 

 has also been ascertained that plants which bear flowers have spiral 

 vessels, and that such as have no flowers are usually destitute of 

 spiral vessels, properly so called; so that the inquiry of the student, 

 instead of being directed in the first instance to an obscure but 

 highly curious microscopical fact, is at once arrested by the two 

 most ob^dous peculiarities of the vegetable kingdom. 



Then, again, among flowering plants two great divisions have 

 been formed, the names of which, Monocotyledons and Dicotyle- 

 dons, are derived from the former having usually but one lobe to 

 the seed, and the latter two, — a structure much more difficult to 

 ascertain than the presence or absence of spiral vessels. But no 

 Botanist would proceed to dissect the seeds of a plant for the pur- 

 pose of determining to which of those di\dsions it belongs, except 

 in some very special case. He knows from experience that the 

 minute organisation of the seed corresponds with a peculiar structure 

 of the stem, leaves, and flowers, the most highly developed, and most 

 easily examined parts of vegetation; a Botanist, therefore, prefers 

 to examine the stem, the flower, or the leaf of a plant, in order 

 to determine whether it is a Monocotyledon or a Dicotyledon, and 

 rarely finds it necessary to anatomise the seed. 



The presence or absence of albumen, the structure of the embryo, 

 the position of the seeds or ovules, the nature of the fruit, the modi- 

 fications of the flower, are not to be brought forward as other 

 difficult points peculiar to the study of the Natural System, 

 because, whatever system is followed, the student must make him- 

 self acquainted with such facts, for the pui'pose of determining 

 genera. The common Toad-flax cannot be discovered by its 



