6 
POPULAR SCIENCE REVIEW. 
the order Balanophorese. The resemblance between the true 
leaves of the Eucalypti , or gum-trees, and the dilated petioles 
or phyllodia of the Mimosce , both presenting their edges instead 
of their surfaces to the sky and earth, and both abundant forms 
of trees in Australia, is very remarkable. The development of 
ascidia or pitchers from the leaf-stalk or leaf itself occurs not 
only in the American Sarracenia and Barlingtonici and the 
Asiatic Nepenthes , belonging to orders at almost the opposite 
poles of flowering plants, but in Bosacese, Asclepiadaceae, and 
several other natural orders. The singular irritability of the 
leaves of the Mimosa pudica , or sensitive plant, and other 
species of Leguminosse, occurs again in another order of very 
little structural affinity, but presenting curious analogies in its 
foliage, the Oxalidese, or wood-sorrel order. Dr. Hooker 
describes and draws, in his “ Flora Antarctica,” a most singular 
species of Galtha (allied structurally to our marsh -marigold), 
whose leaves are almost an exact reproduction of those of the 
Dioncea muscipula, or “Venus’s fly-trap.” In the collection 
of Mr. Saunders is a species of olive, Olea ilicifolia , and a 
variety of the common holly, Rex aquifolium , var. macro- 
carpum , in which the resemblance is extraordinarily close, not 
only in the shape of the leaf and of the spiny teeth, but in the 
very arrangement of the principal veins, and even in the tex- 
ture and colour. Pairs of leaves exhibiting as close resemblance 
may be composed of an Anemone (Ranunculacese) and a Pelar- 
gonium (Greraniacese), a Gnaphalium (Composite) and a 
Lavandula (Labiatse), an Oxalis (Oxalidese) and a Grotalaria 
(Leguminosae), a Gentiana (Grentianacese) and a Veratrum 
(Melanthacese), a Grevillea (Proteaceae) and an Acacia (Legu- 
minosae), a carrot (Umbelliferae) and a Pelargonium (Grera- 
niaceae), and of a Thujopsis (Coniferae) and a Selaginella 
(Lycopodiaceae) ; the last pair comprising a flowering and a 
cryptogamic plant.* 
Nor are we confined to the leaf for the recurrence of the 
same type in widely separated families. The peculiar mode of 
dehiscence of the anther to allow of the escape of the pollen 
known as “ opening by recurved valves ” occurs in the Berberi- 
daceae, in the Lauraceae, and in a single tribe of Combretaceae. 
The pollen grains covered with spiny prominences are found in 
Malvaceae and in some Compositae. But far more curious and 
-striking than these is a remarkable recurrence in several 
orders of an almost identical external appearance of the fruit. 
Any indehiscent fruit with a broad membranous wing is called 
by botanists a 66 samara,” of which we have instances, among 
our own forest-trees, in the elm, the sycamore, the maple, and 
the “ keys ” of the ash. Figs. 4 — 7 represent the form assumed 
* See complete lists in “Nature,” May 26, 1870, and May 4, 1871. 
