Chap, i.] Introduction. zi\ 



these increased powers the attention was concentrated on defi 

 nite points in the object ; what was seen was to some extent 

 indistinct, and always only a small part of the whole object ; 

 perception by means of the optic nerve had to be accom- 

 panied by conscious and intense reflection, in order to make 

 the object, which is observed in part only with the magnifying 

 glass, clear to the mental eye in all the relations of the parts to 

 one another and to the whole. Thus the eye armed with the 

 microscope became itself a scientific instrument, which no 

 longer hurried lightly over the object, but was subjected to 

 severe discipline by the mind of the observer and kept to 

 methodical work. The philosopher Christian Wolff observed 

 very truly in 1721, that an object once seen with the micro- 

 scope can often be distinguished afterwards with the naked 

 eye ; and this, which is the experience of every microscopist, is 

 sufficient evidence of the effect of the instrument in educating 

 and training the eye. This remarkable fact appears also in 

 another way. We saw in the history of morphology and sys- 

 tematic botany that botanists for a hundred years scarcely 

 attempted to make themselves masters in a scientific sense of 

 the external and obvious relations of form in plants, and to 

 consider them from more general points of view. Jung was 

 the first who applied systematic reflection to the morphological 

 relations of plants which lay open before his eyes, and it was 

 not till late in our own century that this part of botany was 

 again handled in a scientific and methodical manner. This 

 extremely slow progress in obtaining a mental mastery over 

 external form in plants on the part of those who are continually 

 occupied with them appears to be due chiefly to the fact, that 

 the unassisted eye glances too impatiently over the form of the 

 object, and the attention of the observer is disturbed by its 

 hasty movements. In direct contrast to this customary want 

 of thoughtfulness in contemplating the external form of plants, 

 we find the first observers with the microscope, Robert Hooke, 

 Malpighi, Grew, and Leeuwenhoek in the latter half of the 



