100. Cycas, Linn.
Sex. Syst. Dioecia, Polyandria.
No product of this genus is employed in Europe, either as medicine or food. From the stems of C. circinalis and C. revoluta a starch is obtained, of which a kind of sago is said to be made in the East. I have prepared starch from both of these species, and find that its microscopic characters are entirely different from those of the sago starch of European commerce. The starch of C. circinalis consists of grains united in masses of from 2 to 6: the single grains are rendered more or less irregular or polygonal by their mutual compression, but hemispherical and muller-shaped particles predominate. Their size varies, but is on the average smaller than that of the starch grains of genuine sago. The so-called hilum frequently appears split and surrounded by rings. In polarized light the grains show a distinct cross. [The following measurements, in parts of an English inch, of the starch of C. circinalis, were made for me by Mr. George Jackson:—Single Grains. 0.0015, 0.0013, 0.0010, Round ... 0.0008 by 0.0007, 0.0005, 0.0004, 0.0003, Hemispherical ... 0.0011 by 0.0009, 0.0007 by 0.0006. Compound Grains. 0.0015 by 0.0008, 0.0013 by 0.0010. Those particles of which one diameter only is given had a circular outline, and were probably muller-shaped grains seen endwise.]
The starch of C. revoluta, of which Japan sago is said to be made, resembles that of the preceding species. None of it comes to England. The Dublin Pharmacopoeia, 1850, states that sago is the farina of the interior of the trunk of Cycas circinalis, and also of other species of Cycas, and various Palmaceae. The facts, however, are as I have stated them.
A clear mucilage, which concretes into a gum like tragacanth, exudes from fresh-wounded parts of several species of Cycas. [Roxburgh, Fl. Indica, vol. iii. p. 749.]