Mav 13, 1909] 



NA TURE 



325 



is moistened, and a roller charged with a greasy ink is 

 passed over it, the ink is taken up by the print more 

 readily where the light has produced the most change and 

 the water has been the least absorbed. The use of rollers 

 for the application of the ink soon gave way in favour of 

 brushes. This process commended itself to many photo- 

 graphers, especially those who desired to " control " their 

 prints, that is, to produce what they desired rather than 

 what they were able to secure by photographic methods, 

 for it is possible to put on much or little ink, and to reduce 

 or increase the quantity in the various parts of the print 

 as the taste of the worker may dictate. Obviously a wide 

 choice of colours is available, and the method has the 

 advantage of giving the peculiar richness and depth of 

 tone associated with oil colours. 



About a year ago it was found possible to render bromide 

 enlargements available for this process, the silver image 

 in the enlargement effecting the reduction of the bichro- 

 mate. Thus no large negative is needed, and no exposure 

 10 light after the bromide enlargement has been made. 

 Mr. F. J. Mortimer calls this last method of work the 

 " bromoil " process, and he has now on .view at the house 

 of the Royal Photographic Society, 66 Russell Square, 

 more than fifty examples of his own work. The exhibi- 

 tion will remain open, free on presentation of visiting card, 

 daily from 11 a.m. to 5 p.m., until June 8. Mr. Mortimer 

 has been known for a considerable time as the producer 

 of fine marine and coast-scenery photographs, but here 

 he shows also landscapes and portraits of various kinds. 

 Those who are interested in such methods of work will 

 ■ get a better idea of the possibilities of the " bromoil " 

 process by a study of these examples than they have ever 

 had an opportunity of getting before. 



Arboriculture in Germany.* 



'T'HE German Arboricultural Society came into existence 

 ■^ in the year 1892, and now has a membership of iSoo, 

 of whom 120 attended its annual meeting in .August, 1908, 

 in Alsace Lorraine ; Strassburg and Colniar being its head- 

 quarters. The president is Count Schwerin, who is ably 

 helped by the secretary, L. Beissner, the conifer expert. 

 The report just issued gives a detailed account of the 

 meeting. The first three days were devoted to the read- 

 ing of papers now published. Then followed visits to 

 private parks, where many fine e.xotic and native trees, 

 some of which are illustrated in the report, were seen. 

 Each member, who was himself listed and conspicuously 

 numbered, received a numbered list of the trees worthy of 

 note in each centre visited. The list gave the name, girth, 

 height, and age of each tree, with further remarks in 

 some cases. 



The lists embodied in the report may serve as an indica- 

 tion of the perfection of arrangement which characterised 

 the meeting. Everything was planned to the minute, and 

 nothing was allowed to interfere with the programme. 

 Thus at OUweiler Prof. Engler was in danger of being 

 left behind after a hurried inspection of a fine specimen 

 of Quercus sessiliflora, 250 years old. La Schlucht 

 and Hoheneck gave a peep into the forests on the slopes 

 of the Vosges Mountains. This district, with Longuemer 

 and Rctournemcr, was also visited by the botanists fresh 

 from the Botanical Congress at .Strassburg, and was fu'l 

 of interest. 



A few only of the articles in the report can be noticed. 

 In addition to many contributions by the president, including 

 -one on the hardiness of certain trees, and one by Beissner 

 on conifers, C. S. Sargent, an honorary member, gives 

 an illustrated account of the Arnold Arboretum, Koehne 

 writes on Taxodium, Forster on exotic trees, Berg oil 

 Pseudotsuga Douglasii in Europe, while St. Olbrich and 

 Hiibner write on trees suitable for avenues and towns, and 

 Sprenger and Rehder on new or rare arboreous plants. 



Following on more than twenty important papers there 

 ai^e many smaller contributions. One of these mav be 

 noticed. Unger, just returned from a residence of twenty 

 years in Japan, proposed the cultivation of Brotissoneiia 



• Mitteilungen der deutsrhen dendroloeischen Geselkchaft. No. 17, 1908. 

 Pp. 285 ; with many illustratinns. (Bonn— PoppeUdorf : L. Beissner, 

 Geschaftsfuhrer der Gesellschaft.) Price 5 marks. 



papyrifcra for the supply of Japanese paper. As twenty 

 degrees of frost is fatal to the plant, Germany was declared 

 by experience unsuitable for the industry. Several pages 

 are devoted to descriptions, in Latin in many cases, of 

 new species or forms. A useful feature is a correspondence 

 section for the supply of information on such subjects as 

 Platanus diseases, and pitch pine. .\ place is also found 

 for reviews of booI<s on trees. Obituary notices appear, 

 including one on John Booth, a Teutonic Scot, who strove 

 successfully to inttoduce e.xotic timber trees into Germany, 

 and one on George Nicholson, of Kew. Altogether the 

 publication is astonishingly rich in contents of wide and 

 general interest, and is very cheap. 



A curious feature of the report is the entire absence of 

 any reference to the many beautiful illustrations, there 

 being sixteen full-page ones and many others incorporated 

 in the text. Members of the Society, by payment of an 

 annual subscription of five marks, obtain the report, certain 

 privileges at the meeting, and supplies of packets of seeds 

 as well as of living plants. This result is mainly due to 

 the enthusiastic devotion and organising skill of the presi- 

 dent, who has personally made all the detailed arrangements 

 for the meeting at Cottbus in 1909, and provided the 

 necessary particulars for two alternative places of meeting 

 in iqio. The society would be delighted, I learnt, to visit 

 the British Isles in the company of British arboriculturists. 

 Cannot this be arranged for by the three British arbori- 

 cultural societies? 



A re-issue of the reports for the year 1892-1901, in one 

 volume of 500 pages, at not more than nine marks, is 

 offered for subscription. T. J. 



GROWTH OF NERVE FIBRES. 

 'T'HE view that each nerve fibre develops as an in- 

 dependent outgrowth from a nerve-cell, finally be- 

 coming united to other tissues (e.g. muscle fibres) in the 

 periphery of the body is associated especially with the 

 name of His, and has been accepted by the majority of 

 embryologists. Those who have worked at the question 

 of nerve repair or have studied the mechanism of the re- 

 generation of nerve fibres which leads to restoration of 

 functions are divided into two camps ; the majority hold, 

 as Waller originally taught, that the nerve fibres grow in 

 a distal direction from the cut stump attached to the 

 central nervous system, ultimately finding their way into 

 the peripheral segment. A minority of researchers hold 

 the contrary view, namely, that restoration occurs in the 

 peripheral segment independently of connection with the 

 central nervous system. 



Within the last year, Mr. Ross Harrison, of Yale, has 

 demonstrated the correctness of the views of His in a 

 very remarkable way. He has actually seen the fibres 

 growing outwards in embryonic structures. Pieces of the 

 primitive nervous tube which forms the central nervous 

 system were removed from frog embryos and kept alive in 

 a drop of lymph for a very considerable time ; the cilia 

 of the neighbouring epidermic cells remained active for 

 a week or more ; embryonic mesoblastic cells in the vicinity 

 were seen to become transformed into striated muscular 

 fibres, and there was therefore no doubt that even under 

 these artificial conditions — rendered necessary for micro- 

 scopic purposes — life and growth were continuing. From 

 the primitive nervous tissue, and from this alone, nerve 

 fibres were observed growing and extending into the 

 surrounding parts. Each fibre shows faint fibrillation, but 

 its most remarkable feature is its enlarged end, which 

 exhibits a continual change of form. This amceboid move- 

 ment is very active, and it results in drawing out and 

 lengthening the fibre to which it is attached, and the 

 length of the fibre increases at the rate of about i micro- 

 millimetre per minute. Those interested in this subject 

 should refer to Mr. Harrison's last paper, published in 

 the Anatomical Record (Philadelphia, December, 1908), 

 where they will find figures representing the growing 

 fibres in various lengths drawn at intervals of half an 

 hour or thereabouts. 



Such observations show beyond question that the nerve 

 fibre develops by the overflowing of protoplasm from the 

 central cells, and thus give us direct ocular evidence in 



NO. 2063, VOL. 80] 



