March 14, 1878] 



NATURE 



389 



digestion proper, as they occur in the stomach and intestines of 

 animals and on the leaves of carnivorous plants, I say it is 

 probable that these processes are only a specialisation ^ of a widely 

 spread power, which may exist in the simplest protoplasmic 

 ancestor of animals and plants. In this case we shall have no 

 right to consider the existence of carnivorous plants anything 

 strange or bizarre ; we should not consider i% as seems sometimes 

 to be done, an eccentric and unaccountable assumption of animal 

 properties by plants ; but rather the appearance of a function 

 which we have quite as much right to expect in plants as in 

 animals. Not that this view makes the fact of vegetable diges- 

 tion any less wonderful, but rather more interesting as probably 

 binding together by community of descent a wide class of phjsio- 

 logical functiims. Let us now pass on to consider the analogies 

 ol plants and animals in a more advanced stage of life. 



Great differences exist among animals as to the degree of de- 

 velopment attained before the young ones enter the world. A 

 young kangaroo is born in a comparatively early stage of deve- 

 lopment, and is merely capable of passive existence in its 

 mother's pouch, while a young calf or lamb soon leads an 

 active existence. Or compare a human child which passes 

 through so prolonged a condition of helplessness, with a young 

 chicken which runs about and picks up grain directly it is out of 

 its shell. As analogous cases among plants, we may take the 

 mangrove and the tobacco plant Tiie ripe seed of the mangrove 

 is not scattered abroad, but remains attached to the capsule still 

 hanging on the mother plant. In this state the seeds germinate 

 and the roots grow out and down to the sea-level, and the plant 

 is not deserted by its mother until it has got well established in 

 the mud. It is due to the young mangrove to say that the con- 

 ditions of life against which it has to make a start are very hard 

 on it. The most intrepid seedling might well cling to its parent 

 on finding that it was expected to germinate on soft mud daily 

 flooded by the tide. Perhaps the same excuse may be offered 

 for the helplessness of babies — the more complicated the con- 

 ditions of life, the greater dependence must there be of offspring 

 on parent. 



Now compare a young tobacco plant with the mangrove. All the 

 help the seedling tobacco receives from its parent is a very small 

 supply of food ; this it uses up in forming its first pair of leaves ; 

 it has then nothing left by way of reserve, but must depend 

 on its own exertions for subsistence. By its own exertions I 

 mean its power of manufacturing starch (which is the great 

 article of food required by plants) from the carbonic acid in the 

 air. In this respect it is like a caterpillar which is formed from 

 the contents of the egg, but has to get its own living as soon as 

 it is born. . 



In many cases there is a certain degree of independence in 

 young creatures, which are nevertheless largely dependent on 

 their parents' help. Thus, young chickens, though able to feed 

 themselves, depend on their mother for warmtti and guidance. 

 A somewhat parallel case may be found among plants. It 

 has been shown that the large store of reserve material in a bean 

 is not all needed for the development of the seedling. It has 

 been proved that well-formed and flourishing seedlings are pro- 

 duced, even when a large part of the cotyledons has been removed. 

 In tact, the store of food in the bean has been said to play a 

 double part in the economy of the plant,^ first, as giving abso- 

 lutely necessary formative material, and secondly, as protecting 

 the young plant in the strugyle wltli other plants, by supplying 

 it with food till it is well established and able to make its own 

 food. This view was fully established by my father,^ who sowed 

 various kinds of seed among grass in order to observe the 

 struggle ; he found that peas and beans were able to make a 

 vigorous start in growth, while many other young plants were 

 killed off as soon as they germinated. 



The young bean is thus indirectly protected by its mother from 

 death, which the severe competition entails on less fortunate 

 seedlings. This kind of protecdon can only in a certain general 

 sense be compared with the protection given by parent to offspring. 

 Nevertheless, a more strictly parallel case may be found among 

 animals. Certain fishes retain the yolk bag, still containing a 

 supply of food, and swim about leading an independent life, 

 carrying this store with them. Among plants, a good case of a 

 retention of a store of food occurs * in the oak. Young trees 



» See Morren, "La Digestion Vegdtale," Gand, 1876; and PfefFer, 

 " Landwinh. Jahrb.," 1877. 



2 Haberlandt, " Schutzeinrichtuagen ia der Entwickelungen der Keim- 

 pflanzen," 1877, p 29. The idea is quoted as originally given by Sachs, 

 Vienna Acad., xxxvii. , 1839. 



3 See " Origin of Species," 6th edition, p. 60. 

 ■* Haberlandt, p. 12, 



possessing woody stems and several leaves may still have an 

 acorn underground with an unexhausted store of food. 



In comparing the lives of plants and animals, one is struck 

 with the different relation which the welfare of the race bears to 

 the welfare of the individual. In plants ic is far more obvious 

 that the aim and object of existence is the perpetuation of the 

 species. The striking and varied development of the reproduc- 

 tive organs in plants is one (actor in this difference. Roughly speak- 

 ing, plants strike us most by their flowers and seed — that is by organs 

 serving the interest of the race. Animals are most striking on 

 account of their movements, which are chiefly connected with 

 the wants of the individual. If a child wants to know whether 

 a stick is a stick or a caterpillar, he touches it, and if it walks off, 

 classes it in the animal kingdom. Of course, I do not mean 

 that the power of movement is a mark of distinction between 

 animals and plants, bat it certainly is a power which is well 

 developed in most animals, and badly developed in most plants. 

 It is the absence of locomotive powers (as opposed to the absence 

 of simple movements) that especially characterises most plants. 

 One sees the meaning of this if one inquires into mode of life of 

 stationary and of locomotive animals. Stationary animals either 

 inhabit the water, or else are parasitic in habits, and live on 

 tissues of plants or animals. In either case the absence of loco- 

 motion has the same meaning. Many aquatic animals derive 

 their food from the minute organic particles floating in the water, 

 so that even though they lead a stationary life, food wUl be 

 brought to them by the currents in the water. Parasitic animals 

 obtain their food directly from the juices or sap of their host, so 

 that they do not need to move about as other animals do in 

 bearch of food. In the same way plants live like parasites on 

 the earth, penetrating it with their roots, and sucking out its 

 juices ; and their food — carbonic acid — is brought to them by 

 the currents of the air, so that like both an aquatic and a parasitic 

 animal, they have no need of locomotion as far as concerns the 

 obtaining of food. 



In the case of many young animals their powers of locomo- 

 tion would be useless unless the eg^js were deposited by the 

 mother in a proper place ; one cannot imagine anything more 

 forlorn than a caterpillar reared from an egg laid anywhere by 

 chance, and expected to find its proper plant. The necessity of 

 finding proper places to lay her eggs implies the necessity of 

 locomotion on the part of the motner. This need of loco- 

 motion is, of coarse, equally a need to the plant, but it is 

 supplied in a distributed way. The seeds themselves become 

 locomotive ; they either acquire plumes to fly on the wind 

 like the seeds of dandelions or they become burrs and cling to 

 passing animals, or are distributed in other ways. Various 

 and strange are the means of transportal adopted by seeds ; for 

 instance, the acorn seems to distribute itself by deliberately 

 trading on the carelessness of creatures which are usually con- 

 sidered its superiors in intelligence. Good evidence exists that 

 young oaks which grow scattered in large number over a wide 

 extent of wild heathy land have sprung from the acorns acci- 

 dentally dropped by passing rooks. In all these cases the young 

 plant has to trust to chance as to what kind of soil it will be deposited 

 in, and this of course accounts for the enormous number of seeds 

 produced by plants. Sime seeds are more fortunate in possessing 

 a kind of mechanical choice or power of selecting suitable places 

 to grow in. Many years ago my father described a plumed seed 

 which, when danaped, poured out a sticky substance capable of 

 gluing the seed firmly t) whatever touched it. Imagine such a 

 plant blown by the wind over some sandy waste ; nothing tends 

 to stay its course till it happens to pass by a region where the 

 soil is damper ; then it sends out its sticky anchors, and thus 

 comes to rest just where it has a chance of germinating 

 favourably. Again, some seeds have a certain amount of 

 locomotive power independent of such external agencies as 

 wind or passing animals. I mean a power of burying them- 

 selves in the ground ; the seeds of grasses are the best 

 known of these self-burying seeds ; and among them the 

 feather-grass, or Sdpa pennata, is the most conspicuous. 

 These seeds possess a strong, sharp point, armed with a plume 

 or tuft of recurved hairs, wfiich act like the barbs of an airow 

 and prevent the seed from coining out again when it has once 

 penetrated the soil. This arrow-like point is fixed at the lower 

 end of a strong awn, which has the remarkable property of 

 twisting when dried and untwisting when wetted. Thus the 

 mere alternations of damp nights and dry days cause the arrow- 

 like point to rotate, and by another contrivance, which it would 

 take too long to go into, the point is pressed against the surface 

 of the ground and actually bores its way into it. Fritz Miiller 



