absorption takes place entirely through hairs developed upon the leaves. In addition to such examples of plants which have lost their roots on account of the functions of the roots being assumed by other organs, there are also plants in which the roots represent the sole FIG. 81.-Taniophyllum Zollingeri with branches adhering to bark. The plant bears a flower and a bud. vegetative organs. In Taeniophyllium Zollingeri (fig. 81), an epiphytic orchid, the leaves are reduced to minute scales and are of no importance in the nutrition of the plant, that function being transferred to the roots which in the form of flat green ribbons, apply themselves closely to the bark of trees. In this case the roots have assumed the S functions of leaves, while in Tillandsia usneoïdes the leaves have taken on the functions of roots. The Podostemaceæ are aquatic plants which live in warm regions attached to rocks in cascades. The stems and leaves are completely absent, the flowers even being produced on the roots. Some of the roots become closely attached to the stones. Others which are green and ribbon-like, float in the stream, and serve for assimilation. § 3. Atrophy from lack of nutrition. In some cases of degeneration, the organs do not lose their functions, but become reduced, merely because adjacent parts rob them of their nourishment. This kind of lack of nutrition which results in local atrophy, must be distinguished from the general limitation of food-supply which is the ultimate cause of all degeneration. The possible amount of food within the reach of any organism is limited, but besides this, the share of the absorbed food obtained by any particular organ or part of an organ may be limited with a resulting atrophy of that organ or part. Atrophy of this kind may be accidental or normal. 1. Parasitic castration.—A good instance of accidental atrophy of this kind is found in Melandryum album where the ravages of a fungus Ustilago antheridarum may produce parasitic castration.1 1 See Giard, La Castration parasitaire in the Bull. Scient. de la France et de la Belgique. 1887, 1888, 1889. Under the influence of this parasitic fungus which makes its way to the anthers, the stamens of the female flowers assume the form of those in male flowers and in consequence the pistils of these flowers abort from defect in nutrition. 2. Severe or prolonged compression of a limb.-A long continued or forcible compression of a limb results in atrophy of its extremity on account of lack of nutrition from the compression of the bloodvessels. 3. Atrophy of the genitalia in neuter bees.-Lack of nutrition is also the cause of the arrested development of the genitalia normal in neuter bees. The neuters of bees and of some of their allies are females in a state of arrested development. In wasps, humble-bees, and hive-bees, it sometimes occurs that the genitalia of these forms develop sufficiently to be functional, thus resulting in the appearance of small females. In most honeycombs two kinds of cells are formed: in the smaller and more numerous cells are placed the larvæ destined to become neuters, in the larger and less numerous those destined to become queens or perfect females. The food of the two sets of larvæ is different; those in the larger cells are given "royal food" a more nutritious substance. When some of the royal food by an accident gets into a worker cell the sexual organs of that larva are developed so that a small female is formed. In this way as many females as may be desired can be produced, and when a hive has lost its queen, the worker bees produce another1 (Lacordaire). Plants afford many instances of degeneration due to defect of nutrition. 4. Atrophy of the superior flowers in Carex.-In the tall spikes of Carex, it frequently happens that the flowers towards the summit are rudimentary, and authorities are agreed in regarding this condition as the result of defect in nutrition. 5. Atrophy of pistils and stamens. Cases of atrophy of the stamens or pistils normal in species may be given. In Fritillaria persica the flowers are disposed in bunches. The lower flowers possess six perianth members, two cycles of three stamens each, and a pistil. In the median flowers the pistil is smaller, and rarely capable of being fertilized. In the superior flowers the degeneration is complete, the pistil hardly being formed. It might be shown 1 The transference of a function is not invariably accompanied by degeneration. Thus, in the functional development of an individual's nervous system voluntary acts which have been repeated frequently become reflex actions, and have their seat in a different region of the nervous system-as, for instance, walking and acquired professional dexterities. It has been sought to explain the development of the instincts of species in this way by supposing that frequently repeated voluntary acts have become inherited reflexes. As pathological degeneration in man frequently affects the higher regions of the brain, reflexes and instincts may persist after loss of voluntary action. In the cases of transference of nervous functions to lower centres the higher centres do not degenerate but remain able to acquire new voluntary functions. that this degeneration is due to lack of nutrition, by removing the inferior flowers from a young bunch, but we are unaware that the experiment has been made. In Viburnum tomentosum (fig. 82) the flowers are arranged in a compound corymb and occur in two forms. The central flowers have a small corolla, five stamens, and a well-developed pistil FIG. 82.-Flowers from the same inflorescence of Viburnum tomentosum. A, sterile flower with rudimentary pistil and no stamens.-B, sterile flower with very rudimentary pistil and stamens.-C, flower with two fertile stamens; the other three stamens and the pistil are rudimentary.-D, fertile hermaphrodite flower. (fig. 82, D). The eight or nine peripheral flowers of each inflorescence have the corolla much larger, but the stamens are absent and the pistil is rudimentary (fig. 82, a). The petals turned towards the outer side are much the largest, and it is not rare for the petals turned towards the inner side to be hardly larger than those of the central flowers. What is important to notice, as it bears out the relation between degeneration and lack of nourish |