360 Dr. H. Johnson on Divergence as the 



gence, and with it the capacity for motion, when they become 

 old, as after flowering. 



Exp. 8. — I bent down two spikes of Lavender {Lavandula 

 Spica), the one being a very young one not yet in flower, the 

 other almost out of flower. The former raised itself up again, 

 the latter did not. The former was divergent, the latter not. 



c. Whilst engaged in the experiments of which I am now 

 giving an account, it was my constant practice to carry a lan- 

 cet about me, and on every known plant which occurred in 

 my rambles to try the effect of that simple experiment by 

 which it is ascertained whether a plant be divergent or not. 

 The list of plants in which this property was so detected is, 

 as before stated, too long for insertion, but I shall enumerate 

 the principal exceptions, which are not numerous. 



1. Juncus conglomerate. Probably every species of Rush. 



2. Iris Pseudacorus; the leaves divided lengthwise through 

 their narrow diameter. 



3. Garden Carnation (Dia?ithus) ; the flower- stem. 



4. Indian Corn (Zea Mays?), culms of Wheat, and other 

 Grasses. 



Now, it is a most curious fact, that none of the plants or 

 parts of plants above mentioned curve up like ordinary di- 

 vergent vegetables. It is immaterial to the different species 

 of Rush in which position their green culms be placed; and 

 they are therefore not endowed with the power of raising them- 

 selves up when laid down. Besides, from their great flexibi- 

 lity and slender form they are little exposed to this accident, 

 and have plenty of successors or neighbours which, springing 

 up around them, supply their place, if they be destroyed. 



2. The leaves of Iris, so far as I have been able to observe, 

 are equally incapable of vital motion as they are of curving, 

 and they are destitute of divergent power, except when divided 

 through their long diameter. 



3. Every monocotyledonous plant with a jointed stem is 

 either destitute entirely of divergence, or possesses it only in 

 a slight degree ; and they are equally without the capacity of 

 curving their stems. Let a culm of one of the Gramina be 

 pegged down horizontally on the ground, and it will gradually 

 raise itself up. But this is not done by curving the stem, as 

 in other plants, but the joints assume an angular figure, and 

 thus the stem becomes erect, as seen in the drawings of a gi- 

 gantic grass, the Indian Corn plant. See figs. 4 and 5. (next 

 page.) 



It is perfectly evident from this, that the moving power 

 resides, not in the stem generally, but in the neighbourhood 

 of the joints. And as the intermediate space (except when 

 very young) is not divergent on division, we have here, in my 



