1806.] ( 155 ) 



PROCEEDINGS OF LEARNED SOCIETIES. 



ROYAI. SOCIETY OF LONDON. 



Mil. VVii LiAM BitANDE has laid be- 

 fore tills k'iimctl body Ibme origl- 

 7uil experiments iiuule on guiacuin, tVoiii 

 wliieli he iiifeis, that it is a i'ubllaiice veiy 

 (liferent iVoni thole which arc denoniiiiat- 

 (■(1 relius, and that it is alio different from 

 •all thole which are enumerated amoni;it 

 balfams, guiii-rclins, iiiims, and extracts. 

 Moft probably, Mr. Brande lays, it it a 

 iubftancc diltinct in its nature from any 

 of thofc above enumerated, in confe- 

 fjucnce of certain peculiarities in the 

 proportions and chemical combination of 

 its conl^itucnt elementary principles. At 

 any rate he regards siuiacum as com- 

 poled of a rehn modified by the vcnc- 

 table extractive principle, and as fuch, 

 it may be denominated an Extra6to Re- 

 fm without impropriety. Mr. Brande 

 has been led to theie conclufions from 

 ohferving the action of different folvents 

 on guiacum, whence it appeared, that, 

 although this fubilanc* pollell'es many 

 properties in common with rclinous bo- 

 dies, it ncverthelefs dilfcrs from them in 

 the ibllowing particulars : — 1. By afford- 

 ing a portion of vciietable extract. 2. By 

 the curious alterations which it under- 

 goes when fubjected to the action of bo- 

 dies which readily comnmnicalc ox^'gen, 

 fucli as nitric and oxy-muriatic acids; 

 aiid the rapidity with which it diifolvcs in 

 tlie former, o. By being converted into 

 u more perfect reiin ; in which rei'peft 

 guiacum bears fomc refemblance to the 

 green refm which conftitutes the colour- 

 ing matters of the leaves of trees. 4. By 

 yielding oxalic acid. 5. By the quantity 

 of charcoal and lime which are obtained 

 i'rom it -^^Jicn fubiected to deitru6tive di(- 

 tillation. " ' ' 



An interefting paper " On the Direc- 

 tion of the Radicle and (lermen duriui; 

 the Vegetation of Seeds,'' was prefent- 

 C'd to this Society by the Frelident, from 

 T. A. Knicut, VA'q. It is luu»wn that 

 in wluitcver polltion a feed is placed to 

 germinate, its radicle invariably makes 

 an clVort to defiend towards the centre 

 of tlic earth, whiKt the elongated ger- 

 men takes precisely an oppollte direc- 

 tion. By iouie thefe effV-i^ft; liavc been 

 accounted for by gravitation ; to afcer- 

 tain tiiis XVIr. Kuiglit commenced a courfe 

 *>f experiments: lie concluded that if 

 i;ravitatioii were the caufe, it could only 

 prcduce tlielh t'lei^ts while the feed re- 

 tuained at rc% and in tije laiuc polition 



relative to the attradtlon of the earth, 

 and that its operation would become lu(- 

 peiided bv coullant and rapid change of 

 the polition of the germinating feed, and 

 tliat it might be counteracted by the 

 agency of centrifugal force. In a ftrong 

 rjll of wat(;r he coullruCted a wheel limi- 

 Jar to thofc ufed for grinding corn, and 

 to this he adapted another wheel, elevcii 

 inches in dianieter, round the circum- 

 ference of which he attached numerous 

 feeds of the garden bean. The radicles 

 of thefe leeds were made to point m 

 every direction, fomc towards the centre 

 of the wheel, ami Others in an oppolite 

 dire(:-tion. The whole was inclofed iu a 

 box, and fecured by a lock, and a wire 

 grate was placed to prevent the ingrcfs 

 of any body capable of imi^cdiiig the 

 motion of the wheels. Tlie water being 

 admitted, the wheels performed fonic- 

 thing more than 1.50 revolutions ia a mi- 

 nute ; and the pofition of the feeds re- 

 lative to the earth was, of courfe, as 

 often perfectly inverted, within the fame 

 j)eri(jd of time, by which it was imagined 

 the inllueuce of' gravitation mult have 

 been wholly fufpended. In a few days 

 the feeds began to germinate : the radi- 

 cles, ill whatever direction tliey were 

 protruded from th.e polition of the feed, 

 turued their points outwards from the 

 circumference of the wheel, and receded 

 nearly at right-angles from its axis. The 

 gcrmens, on the contrai^, took tlic oppohte 

 direction, and in a few days their points 

 all met in tli'' centre of the wheel. Three 

 of thefe plants were futfered to remain 

 on the wheel, and the Hems foon ex- 

 tended beyond the centre of the wheel, 

 but their points returned and met agaiu 

 at its centre. 



IMr. Knight then inftituted another ex- 

 periment, and from them both he fays, 

 " I conceive inyfclf to have fully proved 

 that the radicles of germinating feeds are 

 made to defccnd, and their germens to 

 afcciid, by fome external cauie, and not 

 by any power inherent in vegetable life : 

 and Tfee little leafon to doubt that gra- 

 vitation is the principal, if not the only 

 agent eni]iloyed, in this cafe, by nature. ' 

 lie next endeavours to point out the 

 means by which the fame agent may 

 produce et'fe<^.ts fo diametrically oppolite 

 to each other. 



The I'adicle of a germinating feed is 



increafed in length only by new ])art9 



I'ucceflivcly added to its apex, and not 



U 'i by 



