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interesting pieces of evidence is that brought forward by M. Gaston Bonnier in a long article,-Influence de la lumière électrique continue sur la forme et la structure des plantes,-running through four numbers (78, 79, 80 and 82) of the Revue générale de Botanique, Paris, 1895. In a previous study (Les plantes arctiques comparées aux mêmes espèces des Alpes et des Pyrénées, Rev. générale, VI, 1894, p. 505) M. Bonnier had shown that arctic plants differ noticeably from the same species growing in alpine regions, e. g., in the greater thickness and simpler structure of the leaves, and had attributed this to the feebler light of the arctic region and to the greater degree of moisture. By means of feeble electric lighting and a moist cool temperature he has now been able to produce these differences synthetically in Paris, i. e., to take alpine plants and convert them into arctic ones. He has also shown by experiments on a great many plants, details of which are given, that feeble continuous electric lighting for a period of six months causes decided histological and morphological changes in nearly all of them, except such as grow in the water. Many plates are given in connection with this paper showing morphology and histology of normally grown and continuously lighted plants and the changes in the structure of the latter are frequently so great that no one would believe the sections to have been derived from the same species. About 75 species were experimented on and these belonged to many different families. The structural changes obtained in Helleborus niger, Fagus silvatica, Pinus austriaca, Picea excelsa, and Pteris tremula are particularly striking. To illustrate, in the needles of Pinus the characteristic arms or folds of the cortical parenchyma disappear entirely and there are several other equally striking changes. In Pteris the petiolule under the influence of the continuous electric light takes on an epidermis which is clearly distinct from the subjacent cells, and the cells of which are elongated perpendicularly to the surface of the petiole and are much larger than the neighboring layers of cortical tissue while their walls are not thickened; the cell layers immediately under the epidermis (sclerenchymatic tissue) do not become thick-walled and are rich in chlorophyll; the intercellular spaces in the cortical parenchyma have wholly disappeared; and, finally, there is no endodermis, although it is well developed in the normally lighted plant. The palisade tissue was imperfectly formed in bright electric light and in many cases entirely disappeared in feeble electric light thus confirming what has been believed for some time on other grounds, namely that the development of the palisade tissue of leaves stands in direct relation to the intensity of the light. Additional experiments seemed to indicate that most of
the results obtained were due not to the kind of light but to the grade of intensity. The whole paper will repay careful perusal. The author's main conclusions are given in the following paragraphs, as nearly as possible in his own phraseology: Modifications due to continuous electric light. The organs completely developed in continuous light have the following characters: (1) The chlorophyll is more abundant and is more uniformly distributed in all the cells which contain it under normal lighting. Moreover, chlorophyll grains may appear even in elements which do not contain them in a normal state, in the bark clear to the endodermis, or even in the medullary rays, in the pith, sometimes even to the central cells of the pith. (2) The structure of the blade of the leaf is simplified; the palisade tissue is less distinct or disappears entirely, the epidermis has cells with thinner walls, and the cortical cells lose their special differentiations (transformation into sclerenchyma of the petioles of the fern, reduplication of the membrane of the cortical cells of the needles of the pine, etc.). (3) The structure of the stem is simplified; the bark is less clearly divided into two different zones or even has all its elements alike; the cork is tardy or but little developed, the endodermis is less well defined, or is no longer distinct from the neighboring cells; the cortical tissue, the tissue of the medullary rays, and that of the pith are composed of elements which more nearly resemble each other; the sclerification and the lignification of the pericycle or of the wood fibres is diminished or disappears entirely; the interior calibre of the vessels is often greater; the perimedullary zone and the libre are less differentiated.
It may be added that the structure in discontinuous electric light approaches more nearly the structure in normal light than that in the continuous electric light. Finally, it should be noted that this latter is intermediate between the normal structure and that in obscurity, except the greening. The simplification of structure under continuous feeble electric lighting is, therefore, to be ascribed partly to the continuity of the light and partly to its feebleness. To sum up, a sort of green etiolation is produced by continuous electric lighting, for the two principal characteristics of the changes obtained are the superabundance of chlorophyll and the simplification of the structure.
Somewhat similar results may be obtained by growing plants for some time in weak daylight in the middle of a room and then comparing their structure with that of the same species cultivated in the bright light of a window. Modifications of form and cell structure are still more pronounced if the same plants are grown in total darkness. Anatomical characters are sometimes used in classification and M.
Bonnier suggests that the electric light may be used to determine which of these are most constant.-ERWIN F. SMITH.
A Graft Hybrid.-At a meeting of the Biological Society in Christiana, Nov. 21, 1895, Prof. N. Wille, the well known algologist, exhibited the fruit and leaves of a so-called graft hybrid which is said to have resulted from the working of a pear upon a white thorn (Cratægus oxyacantha L.). This tree stands in the Hofe Torp in Borge Kirchspiel in south east Norway. According to the statement of Herr Apotheker Johns. Smith, of Fredriksstad, the tree is about twenty years old and stood for fifteen years in an unfavorable place without blossoming. It wa then set in a better place and has blossomed and borne fruit for five years. The flowers are like those of the pear tree but somewhat smaller and borne in corymbs like those of Crataegus. The pedicels and the fruit are smooth, but the calyx lobes are triangular and woolly hairy with the tips somewhat bent back. The small fruits (1.5 to 3 cm. long by 13 to 2 cm. broad) are pear-shaped but with the color of Crataegus fruits. The fruits are five-celled and usually with two sterile seeds in each compartment; the pericarp is somewhat firmer than the flesh of the fruit and recalls the so-called stone of the Cratagus fruit, but is by no means so hard. The taste of the flesh is insipid and lies between the taste of the pear and that of the white thorn. All the fruits examined by Prof. Wille contained only sterile seeds, but Herr Apotheker Smith stated to him that he once found a single perfect seed. The leaves of the tree have retained the appearance of pear leaves and do not appear to be changed, but out of the wild stem below the point of union shoots of the white thorn now and then grow out and these have the characteristic leaves of that tree. This account is taken from Biologisches Centralblatt, Bd. 16, No. 3, Feb. 1, 1896. It would add much to the credibility of this case if it could be learned when, by whom, and from what sort of pear tree this white thorn was grafted. A sceptical pomologist suggests that the top of this tree may possibly be the Japanese Pirus Toringo, or some allied species.-ERwin F. SMITH.
Ustilaginoidea. The following note should have appeared in the March number of this journal, p. 226, after BIOLOGY OF SMUT FUNGI, in connection with which it should be read.
NOTE. Since the above was written, Dr. Brefeld has succeeded in discovering the full life history of Ustilaginoidea. The sclerotia, after lying on damp sand for six months, developed an ascus fructification closely resembling Claviceps. Dr. Brefeld's last paper on the subject
may be found in a recent number of Botanisches Centralblatt, Bd. 65, No. 4, 1896. It is entitled, Der Reis-Brand und der Setaria-Brand, die Entwicklungsgleider neuer Mutterkornpilze.-ERWIN F. SMITH.
Respiration of Trilobites. Dr. C. E. Beecher comments as follows on the probable method of respiration of the trilobite genus, Triarthrus. "No traces of any special organs for this purpose have been found in this genus, and their former existence is very doubtful, especially in view of the perfection of details preserved in various parts of the animal. The delicacy of the appendages and ventral membrane of trilobites and their rarity of preservation are sufficient demonstration that these portions of the outer integument were of extreme thinness, and therefore perfectly capable of performing the function of respiration. Similar conditions occur in most of the Ostracoda and Copepoda, and also in many of the Cladocera and Cirripedia."
"The fringes on the exopodites in Triarthrus and Trinucleus are made up of narrow, oblique, lamellar elements becoming filiform at the ends. Thus they presented a large surface to the external medium, and partook of the nature of gills." (American Journal Science, April, 1896.)
A Criticism of Mr. Cook's Note on the Sclerites of Spirobolus. I have read with some interest Mr. Cook's description1 of certain lines found upon the rings of a specimen of Spirobolus marginatus, but I am unable to agree with him in the conclusions drawn from them, nor with his remarks relative to the diplopod segment in general. It seems somewhat surprising that Mr. Cook made no examination of the musculature, either of the specimen described or of any other, to determine whether the lines discovered coincided in any way with lines of muscular attachment, an examination that is necessary to give his conclusions more than a very superficial footing. Had he made the examination, it is extremely doubtful whether he would have found this necessary data, since in more or less closely related forms no lines of attachment corresponding to his lines are to be found.
1 This journal, p. 333.
Indeed there are many facts that he either ignores or of which he is unaware that are far from lending support to his interpretation of the lines. Some of these I have pointed out elsewhere' when considering the subject of the diplopod segmentation. Mr. Cook seems unfortunate in thinking of the greatly overgrown dorsal plate in the diplopod ring as the segment or somite, and in drawing his comparison from the geophilids. Had he examined the conditions occuring in the pauropods and those in Lithobius, Scutigera and scolopendrids, and taken into account some of the ontogenetic facts known regarding diplopods, he doubtless would have plainly seen indications of alternate plates (not segments) having disappeared and of the remaining plates over-growing the segments behind them, so as to give rise to the anomalous double segments. There would then have been no reason for bringing forward the most decidedly unprogressive supposition, namely, that the double or apparently double condition of the diplopod segment is a condition sui generis unexplainable upon general morphological principles.
With reference to his supposition that alternate leg pairs have disappeared even in the geophilids, the case that he has in mind in mentioning the Chilopoda, I must say there is no evidence whatever. To adduce the geophilid condition as evidence is to adduce the thing to be explained. Therefore, I at least am not able to agree with him in saying that this view is no more fantastic than the old fusion idea of Newport, since the latter has some real ground and many favorable appearances in its support, even though it be incorrect.
-F. C. KENYON.
The Sight of Insects.-M. Felix Plateau has been conducting a series of experiments to settle the question as to whether an insect in flight will go through a net the size of whose meshes would offer no obstruction to the passage of the insect. The question has a bearing upon the difference of vision of Insects and Vertebrates. Mr. Plateau's recent experiments would seem to confirm the statement made by him in 1889 that the vision of insects is obscure as to form, and is adapted more to the perception of movements.
The data upon which the paper is based were acquired by means of ingeniously contrived nettings of various shapes, with meshes 26 to 27 millimeters and 1 to 2 centimeters in size. These nets were placed over attractive lures, such as flowers that insects frequent and in other cases decaying animal matter. The results of the author's observations are given in the following conclusions:
The morphology and classification of the Pauropoda, Tufts College Studies No. 4.