214 Retrospective Criticism. 



GREECE. 



Laconia is susceptible of the greatest improvements ; the land there is 

 extremely productive, though, from being badly managed, every kind oi 

 ao-riculture and gardening are in a state of infancy, and the fruits and herbage 

 of all kinds is of a very inferior quality. When it is considered that this 

 defect may be remedied, and that the unwholesomeness of the marshy lands 

 may be removed by bringing thither a considerable number of exotic plants, 

 of which they do not know even the names ; it may be imagined that even the 

 least political commotion, and the smallest change in the usages of the 

 country, have been of service to this part of Greece, and will become bene- 

 ficial to humanity. {Report of the French Expedition sent to Greece.) 



Art. III. Retrospective Criticism. 



Mr. Thompsons Experiments in Vegetable Physiology. — Sir, Every practical 

 man must be pleased to see contributions from the able and experienced Mr. Thompson of 

 Welbeck. It is from such sources we can only expect to derive legitimate information on the still 

 obscure science of vegetable physiology. It can only be illustrated by patient investigation and 

 daily opportunities of witnessing the silent processes of vegetable life. For such investigation 

 Mr. Thompson has peculiar facilities, as well from situation as from characteristic penetration, 

 long experience, and a refined love of his business. 



In reading Mr. Thompson's papers I was forcibly struck with the truth of what has often been 

 said of other matters ; viz. that two observers of the same phenomena will often come to different, 

 and even opposite, conclusions, either as to the causes or effects. This, I regret to say, appears to 

 be the case between Mr. Thompson and myself on the present occasion, and on the same subject ; 

 namely, the circulation, or rather the primary motion, of the sap. We have both seen and 

 studied the growth of the vine, as well within as out of doors ; the flowing of the sap in pruned 

 jr felled birch and other trees ; the facts noticed by Miller and Bliss ; the growth of plashes, of 

 quickset hedges, and felled trees; and, moreover, the well-known circumstance of the bark of 

 oak running sooner at the top than at the bottom of the boles. Strange as it may appear, how- 

 ever, these very circumstances were proofs to me of the ascent, not the descent, of the sap. 



I presume not to justify this my opinion, especially as it is, or seems to be, so directly opposed 

 to that of one who has had, no doubt, opportunities for observation equal, if not superior, to 

 mine ; but the least I can do is to submit to Mr. Thompson the reasons that weighed with me, and 

 served to confirm my idea of the subject. 



That the primary motion of the sap begins at the top before it is in motion at the bottom of 

 the trunk of a tree, is an obvious fact. How then can it be said to ascend ? This question can 

 only be satisfactorily answered bv referring to other, though exactly similar, natural phenomena. 

 Besides the direct motion of fluids, a retrograde motion is also, at the same time, in certain cir- 

 cumstances, observed ; which was a great puzzle even to philosophers, till it was explained by 

 the indefatigable and accurate Franklin : — A dreadful storm once crossed the United States of 

 America. The accounts of its ravages on the line of its destruction showed that it began to lee- 

 , ward, and ended to the windward, of its course ! This was accounted for by Franklin by instancing 

 the effect of opening suddenly one end of a full canal: the motion of the retiring water begins at 

 the outlet, and generates backward till the whole flows out. Such is the case with all ponderous 

 fluids which escape from any confinement, whether canal, trough, pipe, or tube ; and such is the 

 case, I humbly apprehend, with the elastic sap of a tree. It is contained in the tubular structure 

 of the stem ; it is liquified by the vernal heat of the sun, and, as connected with heat, ascends 

 while it is expanded. The bursting buds give way to this internal impulse, and become the outlets 

 to the rising stream. In course, the actual motion is vertical, while it also apparently retrogrades, 

 as Mr. Thompson has truly described it to do. In fact, there is no other way for its escape ; the 

 vessels below are replete with sap, and it cannot be supposed that the roots can discharge into, 

 that which it is their peculiar function to imbibe from, the earth. 



As intimately connected with this curious subject, and which, as Mr. Thompson truly observes, is 

 still " clouded in darkness," I beg to submit a few additional remarks, which may be perhaps wor- 

 thy of regard in physiological researches. I conceive that the sap of plants is a component qualify 

 only, not an organ, nororganisable; it pervades the whole living system, and particularly that part 

 called alburnum, which is the organ of vitality. This last invests the whole internal structure of 

 the plant, is elongated downwards into every rootlet, and upwards into every twig, as well as 

 laterally expanding itself; thereby increasing the volume of the stems. In this the vital gems 

 are seated : in some cases dispersed over its whole surface ; in others at the joints only, as in the 

 vine. The alburnum of one plant readily unites or anastomoses with that of others of kindred 

 nature, as it happens in budding or grafting; it conveys or furnishes the roots of buds already 

 formed (or incipient gems arising from them) into the soil, and retains its vitality, either in a dormant 

 state or in action ; expanding its buds or gems for a considerable time after it has been separated 

 from the system of which it was originally a part. This is exemplified in the instances of the 

 growth of fallen trees, of a- graft inserted on a dormant stock, referred to by Mr. Thompson. 

 The fibrous residuum (if I may so call it) of the alburnum which remains to become hard wood, 

 originates unaccountably. Whether it is an annually expanding body from the first corculum of 

 the seed, or the fibrous descending processes from former buds, is a question which I take the 

 liberty to propose to Mr. Thompson's special notice. That there is a descent of distinct organs, or 

 of distinct qualities, is incontrovertible; but which of the two it is remains to be ascertained. 



That the stock affects the graft or bud in some cases is well known ; but this influence extends 

 no farther than as affecting the vigour of the growth, or the time of ripening the fruit (unless 

 we admit the mysterious report recorded in page 334. of your Fifth Volume now before me, 

 relative to Captain Smith's apple, in the minutes of the Caledonian Horticultural Society) ; but 



