182 



NA TURE 



[June 19, 1 < 



instruments and methods of observation ; and in a Report which 

 has been laid before Congress and printed he has embodied the 

 main results of his journey. The establishments visited were 

 the Observatories of Paris, Neuchatel, Geneva, Vienna, Berlin, 

 Potsdam, Leyden, and Strasburg, and the workshop of Messrs. 

 Repsold at Hamburg. Prof. Newcomb acknowledges the 

 cordial reception he met with from the directors and astrono- 

 mers of the various observatories, and the facilities everywhere 

 afforded him for the execution of his mission. Most interest 

 attached to the great refractor constructed for the Observatory 

 at Vienna by Howard Grubb of Dublin, which was completed 

 in 1SS1, but, owing to various delays, had hardly been brought 

 into active operation at the time of Prof. Newcomb's visit in 

 April 1SS3. Nevertheless he was able to compare it in several 

 respects with the great Washington telescope, which is of only 

 one inch less aperture. He considers that "as a piece of 

 mechanical engineering it reflects great credit upon its designer 

 and constructor." The chief drawback he remarked, the 

 reasons for which were not evident either to him or to Dr. 

 Weiss, the Director of the Observatory, consisted in the failure 

 •of the friction-rollers for easing the motion in declination ; this 

 motion was found much more difficult than in the case of the 

 Washington telescope. Prof. Newcomb also points to the 

 absence of any rough setting either in right ascension or declina- 

 tion, and the imposbibility of seeing the pointing in declination 

 ■except when the observer was at the eyepiece. With regard to 

 the objective he considers, from such observations as he was able 

 to make, that, " if any defects exist, they are so minute as not 

 to interfere in any important degree with the finest performance 

 of the instrument,'' and its proper figuring is rightly considered 

 the most difficult task in the construction of a large telescope. 

 In the workshops of Messrs. Repsold at Hamburg Prof. New- 

 comb had the advantage of meeting M. Otto Struve, and dis- 

 cussing with him the arrangements for mounting the 30-inch 

 refractor intended for the Imperial Observatory at Pulkowa, 

 the most striking feature in which is the absence of friction- 

 rollers from the declination axis ; he describes the system 

 of wheelwork destined to obviate the difficulty of turning 

 so large an instrument either by hand or a rope at- 

 tached to the two ends of the axis, as at Washington and 

 Vienna, owing to the amount of the friction. The eyepiece 

 micrometers, as now constructed by the Repsolds, are commended 

 for their rapid and convenient use. Amongst his general prac- 

 tical conclusions Prof. Newcomb expresses the opinion that in 

 the mounting of instruments of the larger size, in order to secure 

 necessary stiffness with the least weight, the axes should be 

 hollow. He does not consider that it is worth while to attach 

 friction-rollers to the declination axis, unless further experiment 

 should show that they can be rendered more effective than in 

 the Vienna equatorial. The old system of attaching a single 

 finder to that side of the telescope which is opposite the de- 

 clination axis, he remarks, is insufficient in the case of a large 

 instrument, owing to the necessity of setting the opening in the 

 dome not only to the telescope but to the finder, and suggests 

 the desirability of adopting the plan in the Vienna instrument, 

 which has two finders, the one above and the other below the 

 telescope when in the meridian — a plan obviating all difficulty. 

 The Report further explains the principle of the equatorial coudi, 

 or elbow-shaped equatorial, of the Paris Observatory. The 

 Strasburg meridian-circle, "commonly considered to embody 

 the latest conceptions in astronomical mechanics," is noticed in 

 some detail ; Prof. Newcomb thinks a degree of stability has 

 been secured in it which has never before been reached, and he 

 was at much pains to obtain data for comparing the instrument 

 with the meridian-circle at Washington ; its general design he 

 desi ribes as similar to that of the great meridian-circle at Harvard 

 College Observatory, which was constructed by Troughton and 

 Simms of London. The reader must be referred to the Report 

 for other particulars bearing upon meridian instruments. 



The Aspect of Uranus.— In a note communicated to the 

 Paris Academy of Sciences on June 9, MM. Henry state that, 

 observing on very fine nights with the 15-inch refractor, they 

 have satisfied themselves of the existence of two gray belts, 

 straight and parallel, and placed almost symmetrically with 

 respect to the centre of the disk of Uranus, and that, by mea- 

 sures of their direction, they have found an inclination of about 

 41° to the direction of the orbits of the satellites ; they assume 

 that the planet's equator is in the direction of'the belts. Astro- 

 nomers will probably look for confirmation of such an anomaly 

 to our larger instruments. 



THE CONTINUITY OF THE PROTOPLASM 

 THROUGH THE WALLS OF VEGETABLE 

 CELLS 



A MONO the numerous generalisations of modern botany 

 ■^ there are perhaps few that promise to have more important 

 consequences than the recent statements to the effect that the 

 protoplasmic contents of the cells of plants are not entirely shut 

 oft" from one another by the cell-walls, but that arrangements 

 exist of such a kind that more or less delicate strands of proto- 

 plasm pass through from one cell to another, piercing the cell- 

 walls either at numerous points at certain thinner spots, or 

 simply here and there. 



Th. Hartig in 1837 distinguished certain constituents of the 

 bast of phanerogams which we now know as sieve-tubes. In- 

 vestigated later by the same observer and by Mohl, Nageli, 

 Sachs, and Hanstein, the question as to whether the septa 

 between the cylindrical constituents of these tubes are really 

 perforated, or simply studded with thin pits, was set at rest by 

 the demonstration that strands or cords of protoplasmic sub- 

 stance pass through definite pores or passages in the septa or 

 cell-walls. This discovery then became common property, 

 abundantly confirmed, and is now practically demonstrated by 

 students in every properly conducted botanical laboratory : it 

 remained somewhat isolated for many years, however. 



In 1S80 the botanical world was startled by Tangl's discovery 

 that the cells of the endosperm of certain seeds (Strychnos, Areca, 

 &c. ) present a similar feature — that delicate filaments of proto- 

 plasm traverse the cell-walls through fine perforations, and so 

 place the protoplasmic contents of the cells in direct continuity 

 one with another. 



In 1882 Gardiner showed that a similar continuity of the 

 protoplasm exists between the cells of the motile organs of 

 certain sensitive plants, and there can be no doubt that the com- 

 munication thus established through the cell-walls is instrumental 

 in causing the propagation from cell to cell of the stimulus 

 which induces the movement. It thus becomes established that 

 the cell-walls of plants can no longer be regarded as entirely 

 separating off the contents of one cell from those of another ; 

 but that, in many cases at any rate, the idea of the individuality 

 of the vegetable cell becomes as difficult to maintain as did that 

 of animal cells after the first struggles which resulted in the 

 overthrow of the old cell theory. 



Since 1882, Gardiner has succeeded in extending his results, 

 and has shown that the cells of numerous other parts of plants 

 are in continuity in the same manner, by strands of protoplasm 

 passing through the cell-walls. These researches are, moreover, 

 confirmed by Russow for certain cells of the parenchyma of bast 

 and medullary rays ; and there seems little need of hesitation to 

 accept generally the view that the cells of plants are not closed 

 sacs as was formerly believed, but are provided with passages 

 through their walls, through which fine filaments of protoplasm 

 communicate. Such at least results from the observations so far, 

 and especially those of Gardiner, on the endosperms of a large 

 series of plants. It may now be stated, however, that this is not 

 the only evidence to be quoted in support of the above generali- 

 sation. In addition to the observations of Nageli, Pringsheim, 

 and others, pointing out that the protoplasm frequently adheres 

 to the cell-walls so closely at certain places that it may be pulled 

 out into strands, or even break away, leaving portions on the 

 walls, Gardiner has also made observations which confirm this, 

 and which strongly favour the view that the protoplasmic strands 

 are held fast at the points where they traverse the cell-walls. 

 Bower has also observed similar phenomena in the withdrawal 

 of the peripheral protoplasm in plasmolysis. 



Moreover, it has been pointed out that in the case of cells with 

 very thick walls, the thin pits are normally found to meet on 

 opposite sides ; the same is the case with the radiating strands 

 in Vohiox, and where two opposite strands reach the common 

 cell-wall at different angles, they nevertheless meet at a point. 



So far, however, there is no evidence to show whether the 

 continuity of the protoplasmic strands is maintained from the 

 earliest siaycs, or is established later. This, however, is a 

 very important question in connection with this subject, since 

 the answer to it will materially affect our views as to the nature 

 of the cell. If the cell-walls produced in vegetative division are 

 not complete septa, but membranes filling up the interstices 

 between continuous strands of protoplasm, then the continuity 

 .if the protoplasm through the wall of vegetable cells is simply to 

 'I 1 expression of the fact that the entire plant or 



