132 ThomsoiCs Lectures on Botany. 



and his conclusions are supported by direct and convincing appeals to nature 

 and facts. It is impossible, in this review of the performance, to do the 

 author justice, without encroaching too much on the pages of your Maga- 

 zine; I shall therefore pass as rapidly as possible over what remains, and 

 notice only what is new and valuable, or vague and questionable, and 

 which will sufficiently answer the end I have in view. 



Lecture 4. — Vegetable Organisation. All plants are endowed with con- 

 servative and reproductive organs. " An orange tree, bearing flowers and 

 fruit, is an example of all the parts." The root is defined to be " that part 

 of a plant which attaches itself to the soil in which it grows, or to the 

 substance on which it feeds, and is the principal organ of nutrition." 

 {Keith.) 



It is the reservoir of the prepared juice, furnished by the leaves, in all 

 perennial or biennial plants ; is distinguished from bulbs or tubers, which 

 also are reservoirs of the proper juice, as received from the stem and 

 leaves. This was proved by Mr. Knight's experiment on the runner, or um- 

 bihcal cord, of a potato, which, by absorption of coloured water, showed 

 that the runner had descending, but no ascending vessels." Here the lec- 

 turer, as well as Mr. Knight, should have qualified their assertions by the 

 admission, that both bulbs and tubers are produced occasionally without 

 the assistance of either stem or leaves ; and further, that it is at least pro- 

 bable that the whole system of tuberous and bulbous rooted plants is per- 

 fected together by the vital corculum, though not exactly at the same time, 

 (p. 157, 158.) 



Fibrils of roots supposed to be annual Productions. The fact is, all 

 fibrous-rooting plants have active fibrils while in a growing state, but not 

 while stationary. Their direction is downward, but it is ascertained, by an 

 experiment of Mr. Knight, that they may be made to grow upwards, (p. 204.) 

 This is easily accounted for: the delicate fibrils cannot bear full air and light; 

 and therefore proceed in any direction in quest of moisture and darkness. 

 Progress towards moisture or manure (p. 105.) must be accounted for on the 

 same principle that leaves turn to, and shoots protrude towards, light. This 

 curious circumstance, which the lecturer says has been attributed by some 

 to a sentient or instinctive principle, is ascribed by him to the influence of 

 the gaseous qualities of the manure extending beyond its actual place, and 

 so attracting the radicles. 



The next branch of Lecture 5. is on soils, which contains all that chemis- 

 try has elicited on the subject. 



Lecture 6. treats of the stems of plants, their anatomy, &c. ; all which is 

 done most perspicuously, and agreeably to the generally received opinions, 

 elucidated by practical remarks, and divested of many of the fanciful ideas 

 with which previous writers had obscured this part of the subject. There 

 is, however, one very material point, which, notwithstanding it is supported 

 by almost all the most eminent physiologists of the present time, is too 

 abstruse, and liable to objection. It is this : — " The sap is changed into 

 proper juice in the leaf, and returned into the bark, where part of it being 

 poured out in a gelatinous form between the liber and the wood, there be- 

 comes the raw material, from which the new zone of wood, in its state of 

 alburnum, and the new layer of liber, are manufactured by the vital prin- 

 ciple inherent in the living plant." (p. 351.) 



This property of the juice being transmutable into solid timber, is called 

 by other physiologists its " organisable property," and not confined by 

 them to the formation of wood only, but of every organ, root, shoot, 

 flower, and fruit ! 



Before proceeding to show that all this is exceedingly doubtful, it is but 

 j^istice to the lecturer to say that he does not go this length, confining 

 himself only to its being the origin of the ligneous structure, and disregard- 

 ing the proofs that some other botanists bring forward of its validity. His 



