ODOURS OF PLANTS. 805 
movements resemble those of the arms of the old semaphore 
telegraphs, and hence this plant has been termed the Telegraph 
plant. They go on toa less extent even in the dark, and are 
most evident when the piants are in a vigorous state of growth, 
and when exposed to a high temperature. No satisfactory ex- 
planation has yet been given of the direct cause of this move- 
ment. Similar movements have been observed 1 in the radicle 
of many plants. 
b. Not periodical.—These movements occur in the repro- 
ductive organs of a large number of the Phanerogamia. The 
Pressli7se 
Fig.1178. A portion of abranch, with a leaf of Desmodium gyrans. Thelesf, 
which is compound, consists of a large termina’! leaflet, a, a1 two smaller 
lateral ones, 0, ’. There are also two other rudimentary leafiets, marked c, 
near the terminal leaflet. 
stamens sometimes curve inwards separately Pivards the stigma, 
asin Ruta graveolens (fig. 611) and Parnassia palustris; or in 
pairs, as in Sazifraga tridactylites. They afterwards commonly 
return as nearly as possible to their former position. In Passi- 
flora, Nigella sativa, certain Onagracez and Cactacex, &c., the 
styles move to the stamens; while in other Onagracez and cer- 
tain Malvacee, &c., both styles and stamens move towards each 
other. In each of the above the arrangement is one adapted to 
prevent self-fertilisation, as it is protandrous and entomophilous 
(see page 843). 
d. Opvours or PLants.—These are very various in kind, many 
being highly agreeable, others excessively offensive, while ‘others 
again, though pleasant in small quantity, become disagreeable 
in larger amount. The source of the particular odour is often 
a volatile oil or other product contained in the glands or re- 
ceptacles of secretion of the plant; but in some cases no 
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