251 



cular branch of Natural Science, but is equally extended to all, even 

 to those which now seem to stand upon the surest foundation. The 

 grand difficulty, as Schleiden well says, is to state the question cor- 

 rectly — to know positively what we require, and to state our wants in 

 positive terms. The history of every science is this : — 



" Series of facts accumulate, evidently allied in their nature ; if the 

 quantity become considerable, they are collected, in systematic ar- 

 rangement, into a so-called science, but the seeker wanders hither and 

 thither without hold or aim ; material is heaped up, and yet science 

 does not advance one step. Then comes a man, eminently gifted with 

 genius, or frequently even merely one happily favored by accident, 

 and gives definite expression to the problem, for the solution of which 

 men had been tormenting themselves without knowing it ; and now 

 all the mental powers of the inquirers are suddenly directed to this 

 one point. Down fall the barriers in rapid succession, and science 

 advances with giant strides, till she comes again to a point where all 

 progress is obstructed, where everywhere is met a flat and impenetrable 

 wall, and now the same process of development must be repeated 

 anew, in a higher stage, till again a new leader strike on the right 

 place, where the wall rings hollow, and thus betrays the possibility of 

 a further advance." — p. 237. 



In the eleventh lecture we have a sketch of " The History of the 

 Vegetable World," from the first faint indications of vegetation through 

 its successive stages up to the present fair clothing of our earth. 

 Much of this is, of course, conjectural, though the few great land- 

 marks presented to us in the grand stone herbarium of other days war- 

 rant us in believing that in this case conjecture is not far wide of truth. 

 A history of the early vegetation of the earth, must of necessity involve 

 to a certain degree the history of the early ages of the earth itself, its 

 successive changes of climate and its various rock formations ; the 

 following sketch contains an abridged view of the argument. 



" The gradual development of the vegetable world commenced with 

 the simplest plants, and advanced gradually through the succeeding 

 periods to the most perfect plants of our existing vegetation. The 

 structures of the first period correspond to a tropical climate contem- 

 poraneously extended all over the globe, which passed by degrees 

 from the poles towards the equator into the present climatal condi- 

 tions ; and keeping pace with this appeared another change, for the 

 plants of the oldest period, which seem to have been equally distri- 

 buted over the whole earth, by degrees were confined into regions of 

 distribution, and so passed into the great geographical variety of the 



