April 16, 1886.] 



SCIENCE. 



355 



teacher of any other branch ; and restriction of 

 subjects rather than their enlargement is the need. 



It is impossible to discuss the subject of the 

 future of philosophy-teaching in this country with- 

 out reference to the mooted question of ' electives.' 

 It is evident that the great majority of those 

 American colleges that have not introduced the 

 elective system are giving all the time to philo- 

 sophic studies possible, though I do not undertake 

 to say whether or not that time be distributed in 

 the wisest way. In fact, the outside scoffer would 

 probably say that relatively too much time is 

 given them, when all studies are required. It 

 will be noticed that the colleges where least phi- 

 losophy is required are the ones where most is 

 taught, and the ground is most widely covered. 

 Personally, I should not be surprised to know that 

 they are the ones where most vital interest is 

 taken in these studies, save in the instances, 

 happily many, of the smaller colleges, where the 

 philosophic teaching is in the hands of a man of 

 such strong character that the teaching is a lasting 

 power for life in an ethical way, whatever may 

 be said of the strictly technical value of the phi- 

 losophy taught. John Dewey. 



INSECTIVOROUS PLANTS. 



The peculiar insect-capturing habits of certain 

 of our native plants were observed nearly a cen- 

 tury ago, and the belief was then entertained that 

 the peculiar phenomena served some direct object 

 in the plants' economy ; in other words, that the 

 captured insects served as nutritive material. 

 These observations, however, w^ere long forgot- 

 ten, or received but little attention, till, in 1875, 

 Darwin's well-known work on insectivorous 

 plants appeared. Since then a very great impetus 

 has been received by botanists in their study, that 

 has resulted in large additions to the literature of 

 the subject. In a recent paper by the well-known 

 botanist of Jena, Prof. W. Detmers (Nord und 

 sild, 1886, 72, 81), a review of our present knowl- 

 edge is given, from which the following is ob- 

 tained. 



At present it is well known that the function of 

 the green tissue is the absorption of carbonic acid 

 from the surrounding medium under the influence 

 of light, and its decomposition and formation 

 therefrom of organic compounds. Most of the 

 higher plants are capable of complete and perfect 

 development solely by the aid of purely inorganic 

 materials, though in the larger number organic 

 matter may and does form a share of the nutritive 

 material. In the economy of nature this func- 

 tion is a most important one, as plants thus oc- 



cupy an intermediate position between the animal 

 and inorganic kingdoms. 



But some plants are not thus provided with the 

 green or chlorophyl tissue, and are dependent 

 more or less upon organic foods. In some, as the 

 mildews, the power of transforming inorganic to 

 organic substances is wholly wanting ; while in 

 others, as, for instance, certain orchids, such as 

 Neottia nidus avus, the pow r er is much restricted. 

 Likewise the mistletoe, though sufficiently rich in 

 chlorophyl, derives much of its material from the 

 sap of trees upon which it is parasitic. Insec- 

 tivorous plants, in the same way, seem to occupy 

 an intermediate position between those dependent 

 entirely upon inorganic and those which derive 

 their material purely from organic sources. 



The term •' insectivorous,' as applied to plants, 

 is, however, not strictly correct, nor would ' car- 

 nivorous ' be much better. Different forms of 

 animal life are captured by such plants as have 

 received this appellation, and by the aid of 

 secreted juices are digested and absorbed ; but 

 there is no mechanical action except in capturing 

 and holding the objects, and therefore ' flesh- 

 digesting ' would express more correctly the pro- 

 cess. 



One of the best known of insectivorous plants 

 is the ' sundew ' plant (Drosera), species of which 

 are distributed over nearly the whole world. It is 

 small and low, growing about meadowy places, 

 and conspicuous for the sparkling drops of fluid 

 substance that are seen upon its leaves. The 

 leaves, which are about four millimetres in 

 diameter, have upon their upper surface a large 

 number of peculiar tentacle-like organs, as many 

 as two hundred in some cases. The ones in the 

 middle are shorter and upright ; those near the 

 sides, longer and more horizontal. Each tentacle 

 consists of a stem, permeated by a spiral tube, 

 and a glandular head, which emits a drop of 

 colorless, sticky, and stringy fluid. This substance 

 apparently serves to attract insects as well as to 

 retain them when once they have alighted upon 

 the leaf, as it is seldom that they are able to 

 extricate themselves after coming in contact with 

 it. To yet further assure this retention, the leaves 

 possess the power of closing or folding together, 

 brought about slowly by the irritation conveyed 

 through the tentacles. An insect thus firmly en- 

 closed remains till the fluids secreted by the ten- 

 tacular glands have caused its solution, or, more 

 properly, digestion. Any foreign object, be it 

 mineral or animal, will cause the closure of the 

 leaf and the secretion of fluids ; but there is this 

 remarkable difference, — a mineral substance only 

 produces the flow of an acid secretion, while an 

 insect or piece of flesh causes, in addition, a 



