204 SOME MINOR PROHLEMS CONCERNING, ETC. 



in the earth. That the dissemination of the seeds of plants being 

 entrusted to wind, water, animal, or other agencies, introduces an 

 element which it is not possible to calculate. That, although the 

 possibilities of these agencies arc very great, they may not be in con- 

 tinual operation, as there is evidence to show that in some cases 

 plants spread very slowly. That some apparent anomalies in dis- 

 tribution may arise from those plants which are incapable of pro- 

 pagating themselves by seed. 



That the nidus on which a seed falls also affects distribution, and 

 that certain peculiar floras are due to this cause, although Essex may 

 not be looked upon as a typical county in that respect. That the 

 difficulties of plant colonization in Essex as shown by present diffi- 

 culties with raw boulder clay must in earlier times have been very 

 great. 



Then has been noted the similarity and dissimilarity of our Essex 

 wild vegetation compared with certain tracts north and south of the 

 county. 



Lastly, that the hand of man has been instrumental in extinguish- 

 ing certain forms in this locality, and has perhaps been instrumental 

 in saving a few others, but that on the whole there is a diminution of 

 native forms. That man has also circumscribed the area and so 

 brought into more prominent play the factor known as the struggle 

 for life. That the ultimate outcome of this struggle for life, although 

 sometimes checked by the farmer in clearing away rank vegetation, 

 must deprive us of many fragile forms which still survive as rare 

 plants. That our historical knowledge of common species is often 

 very imperfect, and that observations of them should be put upon 

 record in order to detect incipient changes in distribution. 



Recorded observations are infinitesimal contributions to the sum 

 of human knowledge, yet this sum of knowledge goes but a little way 

 in unravelling problems in which life is concerned. Take these 

 problems of distribution for instance. They have their root in geo- 

 logical time, where the evidence is for the most part swept away. 

 Moreover, if we could question every species as to its history, we 

 could not question every individual as to its environment, both of 

 which are indispensable considerations in any acceptable solution 

 of these problems. 



