The middle upright stem contained these side-arms in various numbers and combinations. In five minutes I had a copy of the message, translated into its fundamental characters, as shown on Plate II.
Plate I
The first grass-blade was the simple, upright stem; the second, three leaflets on their stem, represented the upright portion with two arms to the left at the top and middle, and one arm to the right at the top; and so on.
That brought the message down to the simple and straightforward matter of a substitution cipher. I was confident that Benda had no object in introducing any complications that could possibly be avoided, as his sole purpose was to get to me the most readable message without getting caught at it. I recollected now how cautious he had been to hand me no paper, and how openly and obviously he had dropped each specimen into my book; because he knew someone was watching him and expecting him to slip in a message. He had, as I could see now in the retrospect, been conspicuously careful that nothing suspicious should pass from his hands to mine.
Plate II
Substitution ciphers are easy to solve, especially for those having some experience. The method can be found in Edgar Allen Poe's "Gold Bug" and in a host of its imitators. A Secret Service cipher man could have read it in an hour. But I knew my friend's mind well enough to find a short-cut. I knew just how he would go about devising such a cipher, in fact, how ninety-nine persons out of a hundred with a scientific education would do it.
If we begin adding horizontal arms to the middle stem, from top to bottom and from left to right, the possible characters can be worked out by the system shown on Plate III.
