CHAPTER I. 
THE SCOPE AND LIMITATIONS OF COMPARATIVE 
° MORPHOLOGY. 
CONFRONTED with the great variety of plant-types which exist living and 
fossil on the earth’s crust, the Botanist may regard them in various ways 
with a view to reducing them to some general conception of order. He 
may be satisfied with the mere cataloguing and description of the 
divers forms which he is able to distinguish, and with the grouping of 
those together which show characters in common:—this is the work of 
the Descriptive Botanist, and it naturally took the first place in the 
historical development of the science. Or he may attempt to find in 
such similarities of form as are shown by organisms thus grouped 
together some consecutive account of their probable origin :—this is the 
work of the Scientific Systematist, or student of Phylogeny, and it is the 
ultimate aim of all current Morphology. 
In the earlier periods the student of form understood himself to be 
enquiring into the details of the Divine plan, as illustrated in a series 
of isolated creations: and any similarities which species might show 
would demonstrate for him merely the underlying unity of that plan. 
But in these later days he believes that the comparative study of form 
will lead him towards a knowledge of the main lines of descent. 
Contributory to this, which can only result in a balancing of probabilities, 
or often of mere surmises, is the study of the Fossils: Palaeophytology 
gives the only direct and positive clue to the sequence of appearance 
of plant-forms in past time upon the earth. Unfortunately the results 
acquired as yet. along this line of observation are so fragmentary: that 
they do not suffice to indicate even the general outline of the true 
they must for the present’ be used rather as a check to phyletic 
picture :: 
The field is thus left in great 
theories than as. their constant guide. 
measure open to. other lines of enquiry. es 
_.A second line of evidence which bears upon ‘the evolutionary history 
may be derived from the geographical distribution of plants upon the 
