No. 507] BOTANICAL SOCIETY OF AMERICA 1 59 



were peptic or tryptic or whether the curdling power was 

 due to a specific enzyme, apart from the others. 



The complexity of ferment action and the possible co- 

 existence of several distinct enzymes in one secretion was 

 not fully appreciated at that time, and working as Darwin 

 of necessity did, 'he was not in close enough touch with 

 these matters as they then stood to branch out on his own 

 account into very new fields. What he did do was to 

 make a careful and pretty exhaustive empirical study 

 of the action of the excretion of the glands on a great 

 range of substances. If his list of the latter included 

 a number which were immaterial by way of affording new 

 light on the question and a few which, owing to their 

 mode of preparation, gave inconclusive or erroneous re- 

 sults, it matters very little. He proved successfully the 

 main thesis which he maintained, namely, the ability of 

 these insectivorous plants to avail themselves of proteids 

 as food. When one considers how much even to-day in 

 the study of enzymes depends on almost pure empiricism 

 and what valuable results have in the past been obtained 

 by such methods, one does not cavil at Darwin's mode of 

 attack, although at times it may impress one as a bit 

 happy-go-lucky. 



As a detailed study of the habits of an organism his 

 extended observations on Drosera stand out as a master- 

 piece of this kind of work and the collective result of 

 this work may justly be regarded as one of his best pieces 

 of botanical investigation. It is evident from his letters 

 that he took the keenest interest in this plant, which 

 apparently stimulated his imagination and his desire 

 towards investigation as much as any one thing which 

 came under his notice. It was a subject peculiarly well 

 fitted for his type of investigation, for in it he did not 

 require elaborate mechanical aid to arrive at important 

 results and the previous literature on the subject was 

 scanty and for the most part of minor importance. He 

 had an almost clear field and made the most of his oppor- 

 tunity by producing a work which must for all time re- 



