THE society's NOTE-BOOKS. 153 



seems to be the most varied, and crystals belonging to it are to be 

 found of almost every form. The crystals in the leaf of Lathyriis 

 hirsutus and those in most of the Leguminosae belong to this class. 

 Any two or more of the four varieties may occur together in the 

 same plant. The sizes and shapes are not constant, but may all 

 be referred to one or other of these four classes. 



W. H. Beeby and W. H. Hammond. 



Those Sphcer-aphides which are " attached to the cell-wall by a 

 pedicel and resemble in form a blackberry," may be found in great 

 abundance in the leaves of the India-rubber Plant, Fiais elastica. 

 They are best shown i7i situ by cutting thin sections of the leaves, 

 which may be mounted in any way that the preparer fancies. A 

 '•'bunch of grapes " is perhaps a more correct simile for these than 



a " blackberry. 



H. M. J. Underhill. 



Pla?tt Crystals. — I should like to know whether the difference 

 in form between the crystals found in different plants corresponds 

 to a constant difference in the chemical composition of the 

 crystalline matters, or is due to physiological differences only. 

 Of course, the formation of one kind of crystalline matter in one 

 plant, and of another in another, is in itself a result of different 

 physiological action; but there must also be some further difference 

 in the vital condition of the tissues, to cause the crystals to occupy 

 such different positions in relation to the cells, as they do in the 

 different classes. A mere difference in chemical constitution 

 would hardly account for the crystals in one case occupying the 

 interior of the cell, and in another being imbedded in the cell- 

 wall. What is the chemical constitution of the crystals ? 



In the Chickweed leaf, the sinuous shape of the epidermal cells 

 is very curious ; they fit together like the pieces in a picture- 

 puzzle. The epidermic cells on the mid-rib are of a different 

 shape from those on the blade of the leaf. The spiral vessels are 

 also well seen, and their mode of termination ; or, rather, they 

 have no end, but form anastomosing loops, which bend round, and 

 so join on with the bundle in another nervure. 



H. F. Parsons. 



