469 
pels of Balsam is antidromic, in harmony with the phyllotaxy, we 
find that the carpellary “beaks” of Geranium, Pelargonium and 
Erodium, of the same natural order with Balsam, are all dextrorsely 
twisted. In these cases all the individuals of a species, or even of 
a suborder or order of plants, have the same kind of spiralism. 
But the leaves of all these are antidromic. 
As a contrast to this we sometimes find a quasi-antidromy 
within the same plant, or even inthe same carpel. Thus Azdiscus 
has the corollas of flowers on opposite sides of the same branch 
slightly contorted in contrary directions. The pod of the Lotus 
corniculatus and other Leguminosae bursts open through the forci- 
ble curving of its valves into antidromic spirals. Thesame occurs 
in Foosia of Rubiaceae (figure in Engler and Prantl, 4: 4. 46), 
and in the opening with a spring of the cocci of Ricinus. (A 
branch of this in fruit if left over night on a table may next morn- 
ing have all its cocci opened and its seeds scattered about). 
Doubtless this is the dehiscing mechanism of the sandbox fruit of 
fTura, 
The awns of Gramineae usually have secondary twists of func- 
tional significancy. In Axthoranthum a brown dextrally twisted 
base is surmounted by a pale straight seta ; in Danthonia, Stipa, etc., 
the base is a brown ribbon dextrally twisted, and this is sur- 
Mounted by a rigid sinistrorse style. On the application of water 
the basal ribbon straightens out, causing the style to screw its way 
into the soil, into the wool of a sheep, or into the clothing and 
skin of man (witness Captain Cook’s Crew in Australia in 1770). 
This kind of double twist may be termed didromic (as suggested by 
my colleague, Prof. Brackett). It is found in the sete of some 
Mosses (as figured by Sullivant, /cones muscorum, supplement), for 
example, Munaria Americana, Pottiariparia, Rhynchostegium; or 
Some species of the mosses have the upper part of the seta dex- 
trorsely, and others have it sinistrorsely twisted; but we do not 
See the significance of these peculiarities. 
Charles Darwin showed that in some instances this didromic 
Spirality is a physical necessity, as where tendrils must be 
Shortened and yet their extremities are not to be rotated. This 
is the sort of spiral made by the cord-like scape of Vadlisnenia 
_ Spiratis, so pulling down the fertilized carpel without having to 
