American journal of pharmacy . nt in theAlexandria senna they are of equal size, cannot be confirmed byexamination. (See Figs, j; and ./.) Hut whatever number may obtainin either case, it is so inconstant a character as to be of no valueas a discriminating factor. There is, on the contrary, a point ofgreat distinctive valuj to be found in the size and shape of the 304 Alexandria and India Senna. {^•^jire-iSr^- stomata themselves, a feature that was overlooked in the prelimi-nary paper. Here it will be noticed that almost invariably thestomata of the Alexandria senna are smaller and much rounde
American journal of pharmacy . nt in theAlexandria senna they are of equal size, cannot be confirmed byexamination. (See Figs, j; and ./.) Hut whatever number may obtainin either case, it is so inconstant a character as to be of no valueas a discriminating factor. There is, on the contrary, a point ofgreat distinctive valuj to be found in the size and shape of the 304 Alexandria and India Senna. {^•^jire-iSr^- stomata themselves, a feature that was overlooked in the prelimi-nary paper. Here it will be noticed that almost invariably thestomata of the Alexandria senna are smaller and much rounderthan those of the India. References to Figs, i and 4. will makethis clear. Measurements of a considerable number of stomata ineach case gave the following ratio between the longer and shorterdiameters: In Alexandria the shorter diameter bore a ratio to thelarger of 0-84 to I ; in the India, of 0-6 to I. Occasionally stomata of a rounded form may be found in theIndia senna, but they do not look like the Alexandria and are e^. Fig. 5. Alexandria senna, showing number of hairs in a limited area ;d^ hair scars ; e, nebenzellen. larger. At the present state of the investigation, this characterrepresents by far the most characteristic difference between the twospecies and, together with the number of hairs, affords the bestmeans of detecting a mixture of the two in powdered form. The opinion reached by the author in the former paper, that thenumber of hairs shown by the two species is a valuable means ofdistinguishing them apart, is, after yet more careful research, againadvanced. It would seem at first sight that the test proposed bySchneider, i. e., estimating the number of hair scars upon the epi- Am. Jour. PharmJune, 1897. } Alexandria and India Senna. 305 dermis, would be more accurate than counting the free hairs in thepowder; but it is really unreliable, because the distribution of thehairs is not uniform. This objection does not apply to the countin;^
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