TRANSACTIONS OF THE SECTIONS. 147 



cvliiidrica], and tliis appeared to be owing to their having been attached to cases 

 of the Pomatocents arietimis (sometimes called Ditn(pa mhnhta), a Dcntalium- 

 like Annelid. One specimen was attached to a perfect case, others adhered to 

 frf^ments of cases, while the rest bore no trace of attachment and were quite free. 

 In the last-mentioned state they appeared to agi-ee with a drawing and description 

 given by Dr. John.«ton, in his admirable work on British Zoophytes, of a spe- 

 cimen received by him from Professor Edward Forbes, who considered it to be the 

 TurbinoUa borealis of Dr. Fleming. The specimens now exhibited had much the 

 aspect of TurbinoUa or SjiJKe^iotrochi. Cyathina Simthnis not micommon in the same 

 seas where these specimens were obtained, but at a less depth than is above stated, 

 and its usual habitat is on rocks and stones, to which it is permanently attached by 

 its entire base. The explanation offered by Mr. Jetireys for the abnoi-mal form of 

 his specimens is, that they had attached themselves to empty cases of the Povia- 

 tocerus, being the only hard and stationary substances they could find in their 

 unusual habitat (sand), and that when these cases were broken oft', the base of the 

 corals became rounded by attrition against the sand, and they thus assumed their 

 present shape. The first-fonned layers, which constitute the base of the coral, are 

 soon deserted by the animal ; and there appear to be no means of repairing any 

 injmy to that part, much less of the coral reaflixing itself to another prop. Speci- 

 mens of Cyathina sometimes have also a very naiTow base when they are attached 

 to other corals. Mr. Jeffreys observed, that the pecidiarity in question appeared to 

 be the result of a well-known law, or inherent principle of organization, by which 

 a change of external conditions influences to a certain extent the form of animals 

 and plants, and that such modification of fomi is not due to what has been called 

 " natural selection." 



Alsorhing Poiver of tlie Roots of Plants. By Dr, Jessen. 



Dr. Daubeny had established that different species of plants, gi-owing in the same 

 soil, take up therefrom different foods, and contain minerals in different proportions. 

 This selection, it will be said, is made through " vital force " — a convenient phrase 

 for hiding anything that you cannot or have not inquired into. If we went down 

 to the elementaiy composition of the living body, the teim might be defined as 

 meaning the formation and combination of cells. In this sense it coiTesponds with, 

 and has com]iaratively the same range as, the tenn " ciystallizing force " as regards 

 minerals. The force that puts together crystals and that which puts together cells 

 and forms them into lining bodies, is equally an unknown force ; we use for each 

 the term mentioned. Taking " vital force " to mean the formation and combina- 

 tion of cells, the secretive power of plants was thence to be explained. Some 

 ancient philosophers held that plants desired and selected food nearly in the same 

 way as animals. Tliat opinion was long ago given up ; but where is the difference 

 between animals and plants? Men and animals move to food that they want; 

 plants gi-ow for it. This was a point too often overlooked. But animals can move 

 away or cease to take food when satisfied; plants advance their roots amongst 

 their food, and they cannot use the same parts of the same root for obtaining that 

 food a second time. They have, so to speak, to throw out new fibres every time 

 they want food. A sormd rootlet took up fluid, whether nutritive or not, in a man- 

 ner different from an injm'cd one ; and many physiologists and neai-ly fill chemists 

 have experimented on wounded plants, without luiowing it, o'wang to the delicate 

 handling which rootlets require. The absoi-ption goes on by eudosmosis through 

 the bark-cells. Dr. Graham says that by eveiy such process the membrane of these 

 cells is thinned and dissolved ; that the endosmosis is different for every different, 

 membrane ; and that the force of endosmosis is altered not only by the different 

 natm-e of the substances going into the cell, but also by the nature of the sap in 

 the cell itself. The author considers these facts, as made out by Mr. Graham, to 

 be the starting-point of a new era in the physiology of nutrition. No one has yet 

 taken up the matter and pointed out the value of these discoveries ; and it was 

 sufficient at present to point out that Dr. Graham shows that any slight difference 

 in the composition of the membrane, or of the contents of a cell, ■rtII be a sufficient 

 cause for a decided difference in the natme of the food introduced into it. The 

 point of a rootlet is of a very different structiu-e fi'om its upper part. It serves only 



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