38 PHARMACEUTICAL BOTANY 
by a drop of the entire leaf. The stimulus moves up the other 
leaflet with the result that the secondary leaflets close in order. 
In 20 seconds after the stimulus has been applied all of the 
secondary leaflets, are closed. The stimulus is propagated 
through the stem to other leaves.”! (Cf. Figs. 18 and 19.) 
Fic. 19.—Mimosa Spegazzini. After the application of a stimulus. Compare with 
Fig. 18. (After Steckbeck.) 
4. REpRoDUcTION.—Protoplasm also shows a very remark- 
able ability to increase and to give off detached portions which 
retain the infinitely complex peculiarities and properties of the 
original. The process, moreover, may be continued indefinitely. 
These detached portions may be of the nature of sexual cells 
which unite to form a cell called a zygote or odspore from which a 
mature individual develops or of the nature of asexual cells 
detached singly or enmasse which eventually develop into 
mature individuals. 
' “The comparative histology and irritability of sensitive plants” by D. W- 
Steckbeck in Contributions from The Botanical Laboratory of the U. of Pa., 
vol. IV, No, 2, p. 217, 1919, 
