518 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



The tendrils of the Cucumber family, as a rule, have no adhesive 

 pads; but M. Naudin discovered one species, Peponopsis adhaerens, 

 which bore them. Another plant of the same family (Trichosanthes), 

 growing in a frame, had its tendrils accidentally in contact with the 

 brick wall. This at once developed adhesive pads; but it was not 

 known previously to be able to do so. 



It may be added that the tendrils of Cucumbers supported by wires 

 lost their power of chmbing. 



The Sense of Taste. — If we look for organs of taste, we seem to 

 find some analogies with ourselves in insectivorous plants. Darwin's 

 elaborate investigations discover to us that the glands on the tentacles 

 of the Sundew, just as in the case of our own glands, do not secrete 

 any digestive ferments until they can be excited by the presence of 

 some nourishing (nitrogenous) and digestible matter. Moreover, just 

 as we can suffer from indigestion, so many things, such as hair, 

 cannot be digested by these plants. To these must be added fat, 

 oil, starch, and cellulose; for, as it is not the function of our gastric 

 juice to digest these things, neither is it with the Sundew. The 

 glands, so to say, "taste" the difference. It is only nitrogenous 

 matters which they can consume. 



Hence, it was discovered that the ferment is akin to pepsin, and 

 not like the salivary glands which undertake the duty of making starch 

 soluble and digestible. As Darwin has so fully described the process 

 in his book called *' Insectivorous Plants," the reader is referred to 

 that for further information. 



Sensitiveness to Forces. — Besides actual pressures, strains, 

 stresses, &c. , felt by organisms when material bodies are in direct con- 

 tact with them, plants feel the effects of forces when no material body 

 is actually pressing upon them. This is especially conspicuous in the 

 case of gravity, which is always trying to pull every erect plant down 

 to the ground. Since, however, it has to grow upwards, it must resist 

 this pull. It is, therefore, sensitive to the direct action of gravity, and 

 so responds to it by building up the requisite tissues in order to support 

 its own weight, i.e. to resist the downward pull of gravity. It has been 

 shown* that dicotyledonous stems are constructed on the principle of a 

 circular set of girders, the circumferential vascular bundles supplying 

 the flanges, and pith representing the " web." When the former are 

 in close contact they form a compact cylinder, the web being now 

 dispensed with whenever a rapidly growing stem becomes hollow, as in 

 many herbaceous plants. But if they be long, a weakness arises ; for 

 they may be broken sideways by the wind or their own weight. To 

 resist this strain, transverse diaphragms are constructed at the joints, 

 as in a straw. An interesting form of this is seen in some Bamboos, in 

 which the diaphragm is cup-shaped. This allows for a comhined, or 

 circumferential, downward pull, which resists the tendency to break the 

 intemode across above it. In the tropical woody-stemmed climbers, 

 called " Lianes," various mechanical contrivances are adopted to meet 

 * Kerner's Natural History of Plants, p. 724. 



