1820.] Fhyskal Science during the Year 1819. 127 



tificial divisions, he enumerates 49 genera, 11 of which are 

 new. 



Fuci. — Mr. Dawson Turner having discontinued the publi- 

 cation of his excellent History of the genus Fucus, we have great 

 pleasure iu saying, that the Swedish Professor, Agardh, means to 

 continue it. 



2. PHYSIOLOGY OF PLANTS. 



Epidermis of Plants. — Grew, Malpighi, and Mirbel, have re- 

 garded the epidermis of plants as a mere scurf, formed by the 

 action of the air and liglit upon the exterior and pulpy substance 

 of the parenchyme. Mr. Keith, however, [Linn. Trans, xii. 6.) 

 observes, that the epidermis may be observed completely cover- 

 ing the inclosed parts of buds before they have been exposed to 

 the air; and the action of the air is even detrimental to its form- 

 ation in wounded plants : hence, the epidermis is a distinct or- 

 gan, discharging a peculiar function of the vegetable economy, 

 and entirely analogous to the epidermis of animals. 



Leaves. — A paper, by Dr. Macbride of South Carolina, refers 

 the power of the urceolate leaves of sarracenia to entrap insects, 

 to the inverted position of the hairs in the mouth of the tube, 

 which causes them to slip into tlie hollow of the leaf, and prevents 

 their return. A saccharine juice is secreted in the bottom of the 

 leaves which attracts the insects; so that these plants are used 

 as fly-traps by the inhabitants of those countries. Linn. Trans. 

 xii. 



Transformation of Organs.— Auhevt du Petit-Thouars has 

 lately considered the tendency of the parts of fructification to 

 change into leaves. He observes, that all the parts of the flower 

 of verbascum pyramidatum, except the stamens, manifest a tend- 

 ency to change into leaves. The author imagines that all the 

 observations hitherto made on this subject confirm his opinion 

 of the origin of the flowers of plants : according to which, the 

 calyx, corolla, and stamens, result from the transformation of a 

 leafj and the pistill from that of a bud, produced in the axilla of 

 that leaf; the leaves of this bud, agglutinating together, forming 

 the pericarp. The ovules are, according to him, formed by other 

 buds, produced from the former, but whose leaves, insulated or 

 folded together, and incapable of producing other buds of them- 

 selves, form only barren cocci, until they are fecundated by 

 the male oruan. 



rrom the apparent decomposition of the glandular disk in the 

 boopideae, Mr. Brown thinks it may be inferred, that, in many 

 families, the nectarium may be considered as a series of modified 

 stamina, whether it exists as a simple ring, or consists of several 

 bodies, alternating with the stamina, and, in some cases, putting 

 on the appearance of barren filaments. Li/in. Trans, xii. 



5eet^5. — Botanists have generally admitted, that seeds are never 

 produced absolutely naked ; but the systematists have agreed to 



