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14 ON LEMNACEyE AND THE RAPHIDTAN CHARACTER.
To the same effect were the results of my experiments, formerly re-
lated, in which raphidian and exraphidian plants, grown from seeds in
one pot of identical earth, produced and preserved these characters re-
spectively from the very seed-leaves onwards. Surely the whole facts
are cumulative evidence of the intrinsic connection of raphis-bearing
with the cell-life of the species.
In short, as regards the Duckweeds, while Lemna trisulca and L.
minor never fail to produce a good crop of raphides, these crystals are
as regularly scanty in L. polyrrhiza and L. yihha, and so constantly
absent from Wolffia arrliiza as to afford an excellent diagnostic cha-
racter between this plant and Lemna minor.
But there are Orders of plants, both native and foreign, as more
particularly explained by me in the fourth volume of the ' Popidar
Science Eeview,' truly distinguished as raphis-bearers ; that is to say.
Orders of which every true member yet examined has been found more
or less pregnant with raphides, while the species of the next and nearest
allied Orders are as regularly exraphidian. This phenomenon I have
verified so repeatedly in our own flora as to leave little doubt so far on
the subject. For example, in Onagracea we have thus a raphidian
Order ; while, on the contrary, in Hydrocharidacece we have an ex-
raphidian Order standing betAveen its allied Orders which are not less
constantly abounding in raphides.
Endless confusion, however, will continue, unless we carefully bear
in mind the difference between true raphides, spheeraphides, and ciys-
tal prisms, as described in the ' Popular Science Review ' already cited.
Thus, for want of such care, the sphasraphides which abound in some
Telrarjoniacea, Chenopodiacece, and Ilaloi-agacea,—beautiful examples
of which crystals I have described in Sesuvinm, Atriplex, Chenopodiiim,
Loitdonia, and Haloragis, as well as the crystal prisms in the bulb-
scales of certain Onions, often noticed in my papers,— are still some-
times objected to my description of these plants as exraphidian.
Again, the familiar sphEerapjiides and prisms of Cactacea are not true
raphides ; neither are the sphaeraphides and sphferaphid tissue (Ann.
Nat. Hist, for Sept. 1863, plate iv. fig. 13 ; and Aug. and Nov. 186.5)
of Veratrum, Lyllirum and Geranium, Aralia and Rhamnus.
Dhicovery of the RapJudian Character in Systematic Botany.—The
account o"f raphides in the foreraentioned number of ' English Botany '
contains several errors, most of which may have been the compositor's