284 



Fx^RMERS' REGISTER, 



[No 5 



on the other side. The. dtlffM-ence ofllie veiretahle 

 circulation frorn this experimental one, cniisipts hi 

 its heing caused by a liviriu? principle, and not heat, 

 thoup;ii a certain leriiperaiure is indisppn^alde. M. 

 JRappail ternip the operation ol'thif: [irincinle in cir- 

 culatinjr the sap, aspiraiion (meanin'r Hy thip i 

 pomethin^tr !il<e suction or attraction), ;<nd expira- 

 tion (meamng somethmg like expiilFion or repnU 

 BJon), thepidesol'all the'cells ofgroW!n!.rp!anli9 al- 

 ternately aspiring and expiring, or atlracimg and 

 repelling fluids!. ^ 



The membranes of plant?, as we!! ai= the cells 

 composing them, aspire and ex|iire fliudr^; and 

 when these membranes form a tube wiih branches 

 more or lesscnmposed oC iiei-work orreliculations, 

 the fluid forms one contitiuous current in every 

 part of the tube. 



The stems and branches of all plants are form- 

 ed of cells, which from havino; lieen originally 

 globular, expand by grou'th; and by the pressure 

 of other cells expanding around them, take a 

 wedge-like shape, the thin portion forming their 

 point of attachment, or pedicle (hihnn.) The 

 membranes thus formed may be conceived to 

 fcheath each other, the inner sheaths bein<r insert- 

 ed by their wedge-point (kilum) into the sides of 

 the outer ones. These mutually f:heathing mem- 

 branes besides are traversed both across and 

 lengihways by a net-work of vascniarcanals, and 

 consequently the fluid transmitted by each wedge- 

 pomt must necessarily rise along the side next to 

 the part above the wedge-pomt, falling down the 

 opposite side, and asrain rising alonir the part \te- 

 low the wedge-point, or the contniry. At the 

 eame time a portion ol" the fluid is transmitted to 

 the wedge-point of the next enclosed sheathins: 

 membrane, where the circulation will take a simi- 

 lar direction. 



The flow of tlie sap from, the cut ends of a plant 

 may thus be explained; tor on ea<'h cut surlace 

 there will be alternately one-half of" a sheathing 

 membrane, the fluid in which was rising up, and 

 another half in which it was falling down. 



The branches are always inserted by the wedge- 

 points (/ii7a) of their component sheailiing mem- 

 oranes into the trunk or stem, and, consequently, 

 the circulation of the fluid at the junction- is the 

 same as that just explained. 



The sheathing membranes of the root, it must 

 be remarked, do not terminate in the outer sheath- 

 ing membrane or burso of the stem, but penetrate 

 to one of the inner ones, and lience ihe risinj; sap, 

 as yet not organized, is conveyed to an inner 

 sheath. 



The strong attractive power of the tips of the 

 root fibres, through which alone the liquid food of 

 plants is transmitted, may be seen when roots have 

 been forced to grow between stones; for the lips 

 will be found to adhere more or less firmly to the 

 stones, while the other parts of the root are loose 

 and free. In the same way particles of earth will 

 generally be found adhering to the tips of the root- 

 fibres, having been attracted by the suction or as- 

 piration of the epongiole. (G/umie Orgaaique, 

 811, &c.) 



Changes in the Sap. — The preceding are the 

 views of M. Raspail, which further researches 

 may either confirm or refute. The following are a 

 pmall portion of the interesting experiments and 

 observations of M. Biot on the sap and its changes, 

 and these, it may be remarked, wear more the air 



of fact, and look less theoretical, than Raspail'a 

 statements. 



M. Biot first proposed to himself to ascertain by 

 means of circular polarization, the presei;ce of the 

 g-ummy or saccharine principles in the sap of trees, 

 and to trace these principles as connected with the 

 nourishment of the young buds in spring. Some 

 of the fiicts whicli he discovered were very re- 

 markable. 



He pierced with holes, slopintr sliuhtlv down- 

 wards, several species of trees, early in February, 

 —the almond, the birch, the hornbeam, the maple, 

 the ash, the lilac, the mulberry, the walnut, the 

 elm, the poplar, the plane, the willow, the elder, 

 the sycamore, the lime, and the vine, — fitting into 

 each hole a dry reed, with tlie inserted extremity 

 cut sloping, and scarcely penetrating deeper than 

 tJie bark. Tlie other extremity eniered a small 

 phial, suspended by a bit of wire, and luted with a 

 mixture of oil and wax, immiscible in water. The 

 flowing sap was collected in these phials, and 

 when any evaporation of the watery portion oc- 

 curred, from the temperature of' the tree being 

 hiijher than the air, it was condensed whhin the 

 phial. He was not contented with experimenting 

 on one tree of a species, but selected several of the 

 same sort in various positions and exposures; and 

 fie also fixed on the same tree a considerable num- 

 ber of phials, at various heights frcm the ground. 



In the birch he both discovered that the sugar 

 in the sap is not cane, but grape sugar, and also 

 that the sap actually flows progressively from the 

 root to the summit, the flow varying with exterior 

 physical causes, which serve to modify it. The 

 walnut, the sycamore, and the ma|)le, did not in 

 February show any flow of sap; and JM. Biot took 

 advantage of their state of rest lo examine their 

 interior by having a number of trees of these spe- 

 cies cut down on purpose. It was remarkable 

 that the interior of the bircfi trees were found to 

 be without moisture, and even quite dry. while the 

 walnut and sycamore trees were distinctly soaked 

 (imbibe) with moisture, from the inner surlace of 

 the bark to near the central pith. On being 

 pressed, also, the moisture could be squeezed out, 

 and the oozins was most distinct between each of 

 the circles constituting the annual rings of wood. 

 All this was observed while there was no flow 

 from the reeds into tlie phials except in the 

 birch. 



The walnut trees beiian to give a few drops 

 about the 11th of February, in the phials placed 

 about seven inches from the ground. Tlie sap 

 thus collected was not fermentable grape sugar, 

 like that of the birch, but crystallizable cane su- 

 gar, for it gave a strong polarization towards the 

 right, while that of the birch was towards the lefl. 

 The run into this lower phial, after continuing 

 abundant for several days, began to diminish to- 

 wards the end of February, and at length it ceased 

 altogether. The phial immediatel)'- above it, 

 about a yard from the ground, also gave a very 

 small quantity, while all the other phials on the 

 same tree, to the number of eighteen, remained 

 quite dry. 



What appeared most singular, was, that this in- 

 dividual walnut tree was known to be rat her a late 

 one, while another very large one, at a hundred 

 paces distant, known to be about filteen days ear- 

 lier, gave no trace of sap in filteen phials which 

 M. Biot had attached to it. He began, accord- 



