HARDWICKE'S SCIENCE-GOSSIP. 



shrub in a similar manner. Now, how does it come 

 to pass that under such circumstances it is the petals 

 alone that are tinted, while the other parts are green 

 or brown ? Every student of botany is aware that 

 in flowers and inflorescences the chief chemical 

 process which is the expression of their life is called 

 respiration, i.e., oxygen is inhaled and carbonic acid 

 gas given off, the result being that the constituents 

 of the flower are more or less subject to oxidation. 

 In all probability the tannins which metabolise into 

 the pigments, are formed in the cells of the petal 

 itself, wherein they are placed under very favourable 

 circumstances, both physically and chemically, as 

 regards that process of oxidation, to which they are 

 always specially liable. Moreover, the absence of 

 any other pigment (such as chlorophyll, carotin, 

 etc., present in leaves) enables the colouration due 

 to any colour-forming substance whatever existing 

 in the petals to appear in all its native beauty. 

 Certain other constituents of the cell undoubtedly 

 aid and abet in the production of the tints and hues ; 

 but the details of the synthesis cannot be mentioned 

 here. But how is it that one kind of flower is red 

 while another is blue ? In order to answer this 

 question, we must pass on to the next caravan. 



Collecting a small quantity of the flowers of the 

 violet or of the wild hyacinth, we analyse them as 

 before. But here we see immediately that the result 

 of our manipulation is different. Instead of two or 

 three bodies — one acid and two phenols, we now 

 obtain only one body, viz., phloroglucol, which, be 

 it remembered, was also found among the products 

 of our manipulation of the rose. Hence the tints 

 of the latter, being as it were double-based, are much 

 stronger and more vivid than is the case with most 

 other flowers. This phloroglucol is a neutral body ; 

 and the point advanced or suggested here is, that in 

 the former case it is combined with an acid, and 

 hence the colour is red, while in the latter case there 

 is no acid, and hence the blue colour is unchanged 

 in its primitive condition. Every petty dabbler in 

 the subject knows that an aqueous decoction of a 

 pure blue petal is instantly turned red by a trace of 

 acid, and on precipitating the acid the blue colour 

 is restored, and this again may be changed to green 

 by the fumes of ammonia proceeding even from a 

 long way off. 



Turn we now to the consideration of the brilliant 

 yellow decoration of the buttercup or of the allied 

 marsh-marigold. Here we encounter a state of 

 affairs radically and utterly different. There is little 

 use in this case repeating the process of oxidation 

 now familiar to the reader. By doing so with the 

 strong alcoholic extract of these petals, we get a 

 very small quantity of phloroglucol and maybe an 

 equally minute trace of protocatechuic acid, neither 

 sufficient to account for the splendid vividness of the 

 yellow pigments. What, then, can we do ? We must 

 adopt other measures. The colouring-matter is ex- 



tracted by treating with cold petroleum spirit, or by 

 boiling with strong alcohol or ether, and the fat with 

 which it is mixed is saponified by boiling solution of 

 caustic-soda ; the whole is acidified and cooled, then 

 filtered, and the matter on the filter is dissolved in 

 cold alcohol, when the yellow pigment is obtained 

 unaltered by all this rough treatment. This yellow 

 colouring-matter seems to defy oxidation ; it is very 

 permanent, and is apparently of the nature of a 

 resin totally insoluble in water. It is not directly 

 related in any way to the tannins or glucosides, and is 

 possibly secreted from the protoplasm itself, like 

 oil-drops or crystals. Like chlorophyll, it is clearly 

 a product of the decomposition of vitally active 

 proteid organic matter, and is evolved only in plants 

 where such largely exists. My investigations have 

 led me to the conclusion that neither of these brilliant 

 pigments are related to the fats or the waxes ; they 

 must, therefore, be referred to the terpenes or the 

 resin and camphor group of hydrocarbons. It may- 

 be added that their syntheses will never be effected 

 till some chemist not too much engaged in the 

 prosecution of a money-getting patent follows up 

 the study and investigation of the vegetable proteids 

 in a thoroughly systematic and scientific manner. 



THE RHIZOME AND ALLIED FORMS. 



THE Rhizome or root-stock, which is one of the 

 most universal radical structures throughout 

 both Phanerogamia and Cryptogamia, is in its 

 simpler forms little more than a terrestrial rooting 

 stem. Now if we examine its first modifications, like 

 the stolons of many labiate and rosaceous plants, it 

 will be found to consist simply of a prostrate or 

 ascending rooting stem. But when it becomes 

 enlarged and assumes a subterranean habit, its stem- 

 like structure will be more or less obscured, and 

 become more radical in structure, as those of Triticum 

 repens, Avena elatior, Anemone nemorosa, Pteris, 

 Equisetum, and many of the species of Carex. etc. 

 In the rhizomes of Nuphar, Iris, Acorus, and the 

 stem tubers of Hdiauthus tubcrosus and Solatium 

 tuberosum, the stem structure is still less prominent, 

 although plain enough. 



When the rhizome assumes an erect or vertical posi- 

 tion, as in those of Tamus communis, Bryonia dioica, 

 Discorea, etc., its primordial type is very indistinct ; 

 but in the bulbs, and the erect rhizome of Cicuta virosa, 

 the stem structure is still obvious : while in the stem 

 tubers of Bunium, Conopodium, and the tubercules 

 of many orchids, this relation is almost obliterated. 

 The structural analogy of the stem is usually pro- 

 minent in the root-stock, but less so in the conn. 

 The corms of Arum maculatum well illustrate their 

 analogy to the rhizome ; they are, in fact, a rhizome 

 like that of Iris, whose extremity (the terminal bud) 

 is annually elongating, while its other end is con- 



