NOVEMBBE 22, 1895.] 



SCIENGE. 



681 



curio dealers search for them iu a novel 

 manner. This is done by sprinkling with 

 water the pebbles on the beach of Little 

 Traverse Bay. By the temporary polish 

 thus produced, the dealers are enabled to 

 gather the Petoskey stone in a nearly 

 marketable condition for tourists. 



Chaeles Schucheet. 

 U. S. National Museum. 



ANTIDR03IIC FE0BLE3IS. 



In my paper on Antidromy* I have tried to 

 show: (1) that there is a diversity among 

 the individuals of every species of flower- 

 ing plants, some with a tendency to dex- 

 trorse, others to sinistrorse twisting; (2) 

 that this can be traced more or less through 

 the diiferent orders of plants, in the seeds, 

 stem, phyllotaxy, anthotaxy and seed ves- 

 sels; (3) that it is apparently caused in most 

 cases by the place of origin of the annles on 

 the right or left margin of a carpellary leaf. 



The general evidence for this view is to 

 be found at large ; and without going into 

 details, I may say that further observations 

 confirm the conclusions first reached. The 

 article by Professor Beal in the American 

 Naturalist, 1873, with interesting notes on 

 two kinds of spirality in the cones of the 

 same trees of the Coniferse, presented a dif- 

 ficulty when first called to my notice ; but 

 I find that the young cones are homodromic 

 with each other and with the leaf-spirals 

 of the Coniferous trees, whilst the older cones 

 undergo a change by displacement of the 

 scales, resulting in a false antidromy in the 

 same tree. On growing maize-plants from 

 grains taken from one coluinn of an ear, the 

 forthcoming plants are of different kinds. 

 (This is to correct the statement in my for- 

 mer paper.) 



I have not yet been able to extend the 

 law into the higher cryptogams ; though 

 some things in ferns make me hopeful of 

 succeeding with them , as also some of the 



*Torrey Bulletin, September, 1895. 



illustrations in Schimper's Vegetable Pale- 

 ontology and in other books. A few il- 

 lustrations in the books are, I think, er- 

 roneous ; thus Eugler and Prantl give He- 

 licteres (Sterculiacefe) and with carpels anti- 

 dromic on the same plant. I think this will 

 be found erroneous, as I know the same 

 work is wrong in the figure of Erodium, 

 whose fruit-beaks are all and in all plants 

 dextrorsely twisted (that is in the direc- 

 tion of the thread of a screw) ; as are those 

 in Pelargonium. The carpels of these do 

 not appear to be antidromic (though the 

 leaves are so) as between different plants ; 

 and in Impatiens, of the same order, both 

 carpels and leaves are antidromic. Sachs' 

 Botany gives a figure with a wrong spiral 

 for the elaters of Equisetum (and I confess 

 my own sin here) ; they run dextrorselj' in 

 all the plants. 



The spii'als of the oogonium of Chara are 

 always sinistrally twisted, given wrong in 

 Dodel-port's diagram. The peristome of 

 Bai-bula and other mosses, if twisted, is 

 usually dextrorse, and the seta in opposite 

 directions (didromic) in its upper and lower 

 parts. I think the inner peristome of 

 Buxbaumia is sinistrorse. The anchoring 

 cable of Vallisneria is didromic, twisted dex- 

 trorsely above and sinistrorsely below, so as 

 to bring the two ends nearer together by a 

 centi'al turning. The same is true of the 

 awns of Stipa, Danthonia, and many other 

 grasses ; the base being a dextrally twined 

 ribbon and the tip a sinistrorse seta ; when 

 it is wet the basal ribbon unwinds so as to 

 screw the seta into the earth as into the 

 wool of sheep or the clothing and skin of 

 men, as Captain Cook's seamen discovered 

 in the last century in northeastern Austra- 

 lia. These are cases not of true Antidromy, 

 but of Didromy, a double twist in the same 

 organ. 



As mentioned in my former paper, Richar- 

 dia, Iris and Juncus appear to produce anti- 

 dromic plants not merely by seeds, but by 



