172 Prof. Dewey on Caricography. 
this as an optical centre, it will be found that the great lines are 
situated i in relation to it. E and D are equidis- 
tant above and below it; the same observation applies to G and 
B; and also to H and re The only departure from this symme- 
try is in the case of F, which is not symmetrical with C. It 
will be understood that Iam here speaking of one of those spec- 
tra which are formed when a grating or ruled surface is used. 
In this the colors are arranged side by side, according to their 
wave lengths; the centre of the spectrum which is its most lu- 
minous portion, is occupied by the centre of the yellow space ; 
and the light terminates at equal distances in the violet and red. 
Do not these observations lead us to conclude that the cause, 
whatever it may be, that produces these fixed lines is periodic 
in Jts action : 
What that cause in reality is, we have not now facts phages 
todetermine. I would not affirm that the disengagement o 
combustible matter by a flame will always give rise to dark ‘ines 
But this is very clear, that in all those cases, as cyanogen, alco- 
holic solutions of nitrate of strontian, of boracic acid, &c., in 
which these lines are developed, incombustible matter is uni- 
formly disengaged. 
Art. XIX.—Caricography ; by C. Dewey, D.D. 
(Appendix, continued from vol. iv, ii Ser., p. 350.) 
No. 227. C. lagopina, Wahl., No. 37; Tor. Mon., p. 393.— 
C. leporina, Willd. and Good., (not of Lin.)—C. Sachenali 
Schk. Schk., Tab. Y, fig. 79 and Tab. Fff, fig. 1 
Spica composita; spiculis ternis (2-4) confertis inferne stam- 
iniferis alternis ovatis vel ellipticis; fructibus distigmaticis ellip- 
ticis convexo-subconcavis rostellatis vel acuminatis margine obtu- 
sis ore bilabiatis, squama ovata acuta paulo longioribus. 
so m 4-8 inches high, erect, triquetrous, leafy towards the 
; leaves linear, flat, shorter than the culm; spikelets com- 
penky three (2-4), ovate and elliptic, aggregated, clcse-fruited, 
staminate at the base; stigmas two; fruit ovate, convex above, 
and often concave on the under side, smooth, obtuse on the mar- 
git, acuminate, often short rostrate or apiculate, of variable length, 
orifice entire or slightly two lobed ; pistillate scale ovate, ibis 
white and scarious ou the edge, sometimes hot much exc 
half the length of the fruit. 
Rocky ener, Drummond, and agrees with the well 
known plant of the Alps, Norway, &c. By Schk., two plants of 
rey eet were pede. ceed under C. leporina, Willd. 
