531 



SCIENTIFIC SIDE-LIGHTS 



lanet 

 hint* 



and a half, progress was checked by the pres- 

 ence of a large plant of another kind. 

 BEAL Seed Dispersal, ch. 3, p. 13. (G. & 

 Co., 1898.) 



2619. PLANTS IN SUBTERRANEAN 

 CAVITIES Ejected in Volcanic Eruption. 

 In what manner did the solid coverings of 

 these most minute plants and animalcules, 

 which can only originate and increase at 

 the surface of the earth, sink down and 

 penetrate into subterranean cavities, so as 

 to be ejected from the volcanic orifices? 

 We have of late years become familiar with 

 the fact, in the process of boring Artesian 

 wells, that the seeds of plants, the remains 

 of insects, and even small fish, with other 

 organic bodies, are carried in an uninjured 

 state by the underground circulation of 

 waters, to the depth of many hundred feet. 

 With still greater facility in a volcanic 

 region we may conjecture that water and 

 mud full of invisible infusoria maybe sucked 

 down, from time to time, into subterranean 

 rents and hollows in cavernous lava which 

 has been permeated by gases, or in rocks 

 dislocated by earthquakes. It often hap- 

 pens that a lake which has endured for cen- 

 turies in a volcanic crater disappears sud- 

 denly on the approach of a new eruption. 

 Violent shocks agitate the surrounding re- 

 gion, and ponds, rivers, and wells are dried 

 up. Large cavities far below may thus be- 

 come filled with fen mud chiefly composed 

 of the more indestructible and silicious por- 

 tions of infusoria, destined, perhaps, to be 

 one day ejected in a fragmentary or half- 

 fused state, yet without the obliteration of 

 all traces of organic structure. LYELL Prin- 

 ciples of Geology, bk. ii, ch. 24, p. 389. (A., 

 1854.) 



2620. PLANTS OF NORTH AMERICA 

 FOUND IN JAPAN Poison-ivy and Poison- 

 oak Correspondence of Far-off Lands. Our 

 Rhus Toxicodendron, or poison-ivy, is very 

 exactly repeated in Japan, but is found in 

 no other part of the world, altho a species 

 much like it abounds in California. Our 

 other poisonous rhus (R. venenata), com- 

 monly called poison-dogwood, is in no way 

 represented in Western America, but has so 

 close an analog in Japan that the two were 

 taken for the same by Thunberg and Lin- 

 naeus, who called them both R. vernix. ASA 

 GRAY Darwiniana, art. 5, p. 221. (A., 1889.) 



2621. PLANTS PROTECTED AGAINST 

 USELESS INSECTS Slippery Surfaces an 

 Impassable Barrier. Protection [of many 

 flowers against ants is secured] by means 

 of slippery surfaces. In this case, also, the 

 leaves often form a collar round the stem, 

 with curved surfaces over which ants can- 

 not climb. " I have assured myself," says 

 Kerner, "not only by observation, but by 

 experiment, that wingless insects, and nota- 

 bly ants, find it impossible to mount up- 

 wards over such leaves as these. The little 

 creatures run up the stem, and may even 

 not unfrequently traverse the undersurface 



of the leaves, if not too smooth; but the 

 reflexed and slippery margin is more than 

 the best climbers among them can get over, 

 and if they attempt it they invariably fall 

 to the ground. There is no necessity for the 

 lamina of the leaf to be very broad; even 

 narrow leaves, as, for instance, those of Gen- 

 tiana firma, are enough for the purpose, 

 supposing, of course, that the margin is bent 

 backwards in the way described." Of this 

 mode of protection the cyclamen and snow- 

 drop offer familiar examples. In vain do 

 ants attempt to obtain access to such flow- 

 ers: the curved surfaces baffle them; when 

 they come to the edge they inevitably drop 

 off to the ground again. In fact, these 

 pendulous flowers protect the honey as ef- 

 fectually from the access of ants as the 

 hanging nests of the weaver and other birds 

 protect their eggs and young from the at- 

 tacks of reptiles. AVEBUBY Ants, Bees, and 

 Wasps, ch. 3, p. 52. (A., 1900.) 



2622. PLANTS SUPPLIED WITH NI- 

 TROGEN BY MICRO-ORGANISMS Bacteria 

 of Nitrification. Nitrification occurs in two 

 stages, each stage performed by a distinct 

 organism. By one (nitrosomonas), ammonia 

 is converted into nitrite; by the other 

 (nitrobacter), the nitrite is converted into 

 nitrate [in which latter form alone the 

 plant can use it]. Both organisms are 

 widely and abundantly distributed in the 

 superficial soils. They act together and 

 in conjunction and for one common pur- 

 pose. They are separable by employing 

 favorable media. . . . They belong 

 to the soil, river-water, and sewage. They 

 are also said to be frequently present 

 in well-water. From some experiments at 

 Rothamsted it appears that the organisms 

 occur mostly in the first twelve inches, and 

 in subsoils of clay down to three or four 

 feet. In sandy soils nitrification may prob- 

 ably occur at a greater depth. NEWMAN 

 Bacteria, ch. 5, p. 158. (G. P. P., 1899.) 



2623. PLANTS WITH GOOD INTEN- 

 TIONS A Relapse into Parasitism The Dod- 

 der. There are certain plants the dodder, 

 for instance which begin life with the best 

 intentions, strike true roots into the soil, 

 and really appear as if they meant to be 

 independent for life. But after supporting 

 themselves for a brief period they fix curious 

 sucking disks into the stem and branches 

 of adjacent plants. And after a little ex- 

 perimenting, the epiphyte finally ceases to 

 do anything for its own support, thenceforth 

 drawing all its supplies ready-made from 

 the sap of its host. In this parasitic state 

 it has no need for organs of nutrition of its 

 own, and Nature therefore takes them away. 

 Henceforth, to the botanist, the adult dodder 

 presents the degraded spectacle of a plant 

 without a root, without a twig, without a 

 leaf, and having a stem so useless as to 

 be inadequate to bear its own weight. 

 DRTJMMOND Natural Law in the Spiritual 

 World, essay 9, p. 285. (H. Al.) 



