42 
THE NATURALISTS’ JOURNAL. 
In the common Barberry {Berberis vulgaris), and other plants 
of the same genus, the sensitive properties are to be found in 
the stamens. If we take a well opened flower, the stamens will 
be seen to rest closely against the petals, but on touching the 
base of one of them with the point of a pin, it will spring forward 
with great rapidity and rest against the pistil, at the same time 
discharging the pollen. 
If several stamens are touched simultaneously, these will of 
course all fly towards the pistil, but those which have not been 
touched will remain stationary. The common Barberry is found 
in hedgerows; the ash-leaved Barberry of our gardens is fur¬ 
nished with similarly sensitive stamens. The pretty little Rock- 
rose or yellow Cistus ( Helianthemum vulgare) affords another 
example in point. It occurs in dry pastures and on chalky banks, 
and at first sight the flower is not unlike that of the common 
roadside Potentilla, but the plant is readily distinguished by its 
woody growth and smallish oval leaves, more or less hoary on 
the under side. The flowers only open in sunshine, so that a 
sunny day is necessary for showing their sensitive properties. 
In this case the stamens, which are very numerous, move 
exactly in the opposite way to what they do in the Barberry. 
When the flower is open the stamens are crowded pretty closely 
round the pistil, but on touching them near the base they will 
bend outwards till they lie down on the petals; and there is 
this further difference that they move slowly instead of quickly. 
The movement however is well marked, and, as in the Barberry 
is confined to those stamens which have been touched. It may 
be well shown by pinching the stamens between the fingers. 
The stamens of many composite plants of the Thistle tribe 
are also sensitive, and among these the large dark purple-red 
flowers of the Knap-weeds, ( Centaurea nigra and C. scabiosa ) so 
common on banks and in hedges, exhibit this effect very well. 
Now in all Composite the stamens are united together by their 
anthers into a ring ; a property which led the great Linnaeus to 
classify them in a separate class, by the name of “ Syngenesia.” 
This coherence effectually prevents the stamens from bending 
inwards or outwards, so that their only possible alternative is 
together to move up or down, and this is just what they do. As 
soon as any of the stamens in one of the florets have been touched 
the anthers are drawn down towards the base of the pistil and the 
style remains fixed, thus the pollen is pushed out in little masses. 
I have just tried the same experiment with a flower of “ Sweet 
Sultan/' a garden annual nearly allied to the Knap-weeds and in 
this also the downward movement of the anthers and the protru¬ 
sion of the pollen were well shown. 
The wall Pellitory ( Parietaria officinalis ) is a small branching 
herb of the Nettle tribe. It has oblong downy leaves with entire 
margins, and insignificant whitish green sessile flowers in clusters 
