326 



assuming a more perfect spherical form, and become bounded by an investing capsule, 

 which turns of a rich brown colour, while the contained granules retain their original 

 green. 



"It is difficult to imagine what purpose is intended to be answered by such a change 

 taking place after all circulation and other evidences of life in the plant have ceased. 

 Yet the idea of such a change being the result of a merely fortuitous arrangement of 

 the component particles of the plant attendant on decomposition, is negatived by the 

 circumstance of the remarkable unifonnity and symmetry of the resulting globules, 

 which appear to possess the most defmite characters, differing from each other only in 

 size. Nor is the change by any means uniform for the whole plant ; for in some parts 

 two of the joints were observed to be in the green state, while the joint situated be- 

 tween them was free from green matter and contained the brown bodies : but this 

 might have resulted from the circulation ceasing earlier in the central joint, and con- 

 sequently allowing more time for the changes to take place."— p. 23. 



V. — On the Structure of some Tissues possessing Hygrometric Propertiest 

 By E. J. QuEKETT, F.L.S., B.S., &c. 



Mr. Quekett cites many interesting examples of hygroscopic pro- 

 perties as exemplified in Mosses, Lycopodium lepidophyllum, the 

 seed-vessels of Epilobium, Mesembryanthemura, Rhododendron, Ge- 

 ranium, Banksia, Hura, Avena fatua &c. He then details the struc 

 ture of the capsule of Cerastium, which we give in his own words. 



*' Let us take, for example, the capsule of some plant of the order Caiyophyllese, as 

 Cerastium, and it will be found that when that organ approaches maturity, the apex, 

 which was pointed and entire, will open by splitting into five equal valves, which curl 

 outwards, making one complete coil, and always in the same direction ; by the appli- 

 cation of moisture the valves will resume their original position, and when dry take on 

 the curled fonn again. 



" If one of these valves be examined it will be found to be thin and diaphanous 

 where it forms part of the body of the capsule, but where it is hygroscopic it is horny 

 and opaque. When a section taken from the edge of the valve or curled part longi- 

 tudinally is examined by the microscope, it will be found that the tissues will be dif- 

 ferent on the exterior and internal surfaces, both however cellular ; but the inner layer, 

 or the cells of the convex border, are of different dimensions from the outer, being nei- 

 ther so large nor having so thick walls, (though they are thicker than ordinaiy cells) ; 

 whilst those of the outer layer are almost solid, and the only cavity they have is indi- 

 cated by thin spaces between a series of lines, the chief one of which is in the direc- 

 tion of the longer axis of the cell, the others connected to it at right angles. These 

 cells are of most curious structure, and form an interesting object for the vegetable 

 anatomist. 



" In this arrangement of parts it must be evident that by the shrinking of the tis- 

 sues of the seed-vessel by loss of moisture, there will occur unequal contraction, and 

 that side will be curved which contracts the most forcibly, and by this curvature one 

 valve must necessarily be removed from the next, evidently showing that the tissues 

 act as unequal antagonists to each other.'' — p. 26. 



Mr. Quekett gives numerous instances in which the great end of 



