2 MANUAX OF BOTANY. 



Botany ; this considers plants in their relations to one another, 

 and comprehends their arrangement and classification. 4. Geo- 

 graphical Botany is that which explains the laws which regulate 

 the distribution of plants over the surface of the globe at the 

 present time ; and 5. Palceontological or Fossil Botany is that 

 department which investigates the nature and distribution of 

 the plants which are found in a fossil state in the different 

 strata of which the earth is composed.* 



Distinctions between Animals, Plants, and Minerals, — 

 Botany being the science which treats of plants, we ought to 

 commence our subject by defining a plant. No absolute defini- 

 tion can, however, be given in the present state of our know- 

 ledge of the organic world, neither is it probable that, as our 

 knowledge increases, such will ever be the case ; for, hitherto, 

 the progress of inquiry has showTi that there is no distinct line 

 of demarcation between plants and animals, the one passing 

 gradually and imperceptibly into the other ; indeed, there are 

 observers of repute who maintain that there are certain organ- 

 isms which are animals at one period of their lives, and plants 

 at another, and vice versa. The recent investigations of De Bary 

 have an important bearing upon this point, for he has described 

 certain Fungi, the spores of which, when germinating, give rise 

 in some instances to a body not distinguishable from the Amoeba, 

 one of the lowest forms of animal life. It has also been recently 

 shown that the protoplasm of the spores of the Potato mould 

 {Botrytis infestans) is at times ultimately resolved into active 

 zoospores undistinguishable from some Infusoria. The gonidia 

 of certain Lichens have been also stated to give rise to similar 

 bodies. We have, it is true, no difficulty in distinguishing a 

 plant from a mineral, although, at the present time, there are 

 many naturalists who even dispute this, and believe that simple 

 organisms can be formed out of inorganic matter ; but notwith- 

 standing the ingenuity with which these views have been sup- 

 ported, we must hold such notions to be purely speculative, and 

 continue to maintain that the possession of individual life and 

 power of reproduction in the former, form at once, -without 

 further investigation, a broad and well-marked hne of demar- 

 cation from the latter. Even when we compare a plant with an 

 animal, so long as we confine our researches to the higher mem- 

 bers of the two kingdoms, the distinctions are evident enough ; 

 difficulties only occur when we look deeply into the subject, and 

 compare together those bodies winch are placed lowest in the 

 scale of creation, and stand as it were on the confines of the 

 two kingdoms. It is then that we find the impossibility of laying 

 down any certain characteristics by which the two may be abso- 



* The first three departments are those only that come within the scope of 

 the present work ; the latter being of too special and extensive a nature to 

 be treated of in this manual. 



