CONTEAST BETWEEN THE TWO HOOKEES 421 



but he co-ordinated previous results and denned the limits 

 of distribution of species : thus giving more coherent treat- 

 ment to the vegetation of vast areas of the earth's surface. 

 It is interesting to compare his systematic method with that 

 of his father. The elder Hooker, true to his generation, 

 treated his species as fixed and immutable. He did not 

 readily generalise from them. His end was attained by their 

 accurate recognition, delineation, description, and classifica- 

 tion. His attitude towards microscopic detail is noteworthy. 

 He remarks in his ' Genera Filicum ' that Presl ' has laid too 

 much stress on the number and other circumstances con- 

 nected with the bundles of vessels in the stipes which in the 

 herbarium are difficult of investigation.' Occasionally he 

 gave his reasons for this opinion, as in a notable passage in 

 his ' Species Filicum ' (vol. iii. p. 3), where he explains that a 

 grouping based on the microscopic details of the annulus 

 in Ferns ' would be inconvenient to retain in a work whose 

 main object is to assist the tyro in the verification of genera 

 and species : and natural habit is often a safer guide than 

 minute microscopic characters.' Thus we see that for the 

 elder Hooker convenience of diagnosis was more important 

 than details of structural similarity. 



But the younger Hooker, while he was not a whit behind 



the best of his predecessors in the recording and tabulation 



of detail, saw farther than they. He was not satisfied with 



the mere record of species as they are. He sought to penetrate 



* the mystery of the origin of species. To the elder Hooker 



species were units. The younger contemplated the summing 



of those units into progressions, which would thus in a sense 



make visible the changes in descent. To the elder Hooker 



the study of plants was static. In the hands of the younger 



it became' dynamic. Development and microscopic detail, 



used according to the methods of Schleiden and Hofmeister,' 



became then of the first importance. Such enquiry we see 



illustrated in those of Sir Joseph's writings which may be 



i styled Morphological. The great outburst of systematic work 



j,in Britain in the middle of the nineteenth century had had a 



J deleterious effect on those of lesser breadth of view than he. 



