THE CHEMISTRY OF SOME COMMON PLANTS. 



P. O. KEEGAN, LL.D., 

 Patterdale, Westmorland. 



It is with much pleasure that I am now able to contribute 

 a further instalment of the paper on this subject which was 

 published in 'The Naturalist ' for February 1897. There is no 

 need to rehearse the ideas and reasons stated therein for the 

 special study and consideration of a department of botanical 

 science so fraught with interest and yet so frequently ignored 

 and perhaps contemned. Unquestionably the pursuit of plant 

 analysis is difficult, and demands considerable experience, but 

 after all a careful and systematic method of work is the grand 

 desideratum. The petty alertness of the ' splitting ' systematist 

 is hardly needed. What is imperatively demanded is, so to 

 speak, the collation of the memorials of what have gone before 

 with the results and conclusions to be justly drawn from the 

 experiment just befqre your eyes. However, I propose now to 

 select certain prominent and familiar examples of certain orders 

 of plants, commencing with the 



Bracken. Pteris aquilina. Most of us no doubt can exclaim 

 with Wordsworth, 4 How often I have marked a plum}- fern,' but 

 how many of us ever try to detect the similarity or to discover 

 the difference between the frond and the leaf. Anatomy here 

 aids us greatly, but chemistry is more than one better. Accord- 

 ingly we analyse the fronds or the frondlets at different periods 

 of growth, say in May, August, and October. In May the 

 results vividly recall those obtained on the examination of any 

 of our forest leaves ; for a very eminent feature is the presence 

 in the frond of a large quantity of rutin, and, moreover, the 

 indications of the predominance of proteid substances are mani- 

 fested in every way, e.g., the ready detection of the nitrogenous 

 compounds, the enormous proportion of potass, and of phosphoric 

 and sulphuric acids in the ash. In August, i.e., the period of 

 mature development of the frond, we find a change, for now we 

 detect about 1 per cent, of wax, 5 resin, 6 to 10 tannin, 

 10 mucilage, over 40 fibre, and 6*i ash. The amount of carotin 

 is considerable, starch is abundant, but the rutin is now nearly 

 all gone, and the tannin is extremely similar in its reactions to 

 that of many of our forest leaves, i.e., it is a catechol tannin 

 yielding- on potass-fusion protocatechuic acid and phlorogtucin. 

 So far the similarity to the dicotyledonous leaf is complete. 

 Nevertheless, there is a very serious difference, inasmuch as we 



1902 May 1. 



