February 6, 1908] 



NA TURE 



example, a parabola can be found differing but little from j 

 sin X. To show that the stresses .v.\- and zz are widely j 

 different in a plate dam and in a complete dam, it would ; 

 therefore seem essential to integrate the two equations ! 

 given by Prof. Pearson in his last letter, and to compare 

 these integrals, or else to decide the matter on other j 

 considerations. The integration is, I understand, imprac- 

 ticable, and this being so, the argument in my letter of j 

 January 2 would seem to apply. It was to the effect that 1 

 if in the case of a plate it is permissible to write 1 

 xy = yz — yy throughout, then to the same order of 

 approximation the stresses ;: and .v.v are the same in the 

 plate dam and in the actual structure. If the stresses Ay 

 and ys are zero in the case of the plate, then the stresses 

 yy which are developed when the lamina forms part of the 

 complete structure cannot, themselves, give rise to any 

 such shears as xy, ys, or zx, and as the dam is not con- 

 strained at top or flanks, it is difficult to see how, in the 

 absence of these shears, the stresses xx and zz can be 

 affected. Certainly not by the 30 per cent, which Prof. 

 Pearson gives as the order of the error. 

 83 St. James's Road, Croydon. H. M. Martin. 



SOME SCIENTIFIC CENTRES. 



No. XII. — TiiK BoT.^Nic.Ai. Institute of the 



Lniversity of Bonn. 



'pHE traveller visiting the well-kept Rhenish city 

 ^ of Bonn, on taking a stroll down the beau- 

 tiful Poppelsdorfcr .\llee, finds al the end of this de- 

 lightful avenue a large square building within an 

 enclosure, the Poppclsdorfer Schloss. This building, 

 which is two stories high, enclosing a circular court, 

 bears no external evidence of containing within its 

 walls a great centre of biological research, for the 

 edifice was originally a palace, having been used up 

 to the beginning of the last century as a summer 

 residence of the electors of Cologne. The building is 

 now owned by the university, and is occupied by the 

 biological laboratories and the natural history 

 museuiTi. The rooms of the second floor on the north- 

 east and south-east sides are occupied by the botanical 

 laboratories and by the residence of the professor in 

 charge, one of the greatest botanists of all times, 

 Geheimralh Prof. I'^douard .Strasburger. 



The young botanist who is familiar with the writ- 

 ings of Prof. Strasburger, and has formed some idea 

 of this famous botanical institute, on entering the 

 laboratories for tlie first time is only surprised and 

 perhaps disappointed, for he sees little that suggests 

 a modern and well-equipped laboratory. The fact 

 that the building was erected in the first half of the 

 eighteenth century, ;ind for another purpose, explains 

 whv the rooms are not well adapted for their present 

 use. However, the windows are large, and since 

 there is ample room for apparatus and materials, th< 

 investigator has little cause for complaint. 



The Botanical Institute includes an elementary 

 laboratory, one for advanced students, a large lecture 

 room, and rooms for assistants and the professor 

 extraordinary. The lecture room is provided with a 

 profusion of charts and diagrams for illustrative pur- 

 poses. The rooms adjoining the laboratories on the 

 south-east side of the building are occupied by the 

 professor as a residence. Two rooms of his residence 

 Prof. Strasburger devotes to his own work, one 

 serving as a laboratory and the other as a library. 

 In these rooms, which are plainly furnished, every- 

 thing is orderly arranged and kept scrupulously clean. 

 The library contains, in addition to files of 

 periodicals, all the important works on morphology 

 and cytology. Perhaps the most valuable part of the 

 library is the series of reprints on histological sub- 



No. 1997, VOL. yy] 



jects. A copy of almost every cytological paper pub- 

 !:shed, whether treating of animal or plant, is tu be 

 I Dund here. , ., 



The principal windows of the laboratories and of 

 .he residence overlook the palace garden, which has 

 been the botanic garden since the founding of the 

 university. The garden, though small in area, is well 

 stocked and rich in flowering plants. The latter 

 occupy the central part of the grounds, which are care- 

 fully laid out and arranged according to the system 

 of Eichler. On either side of the central part is the 

 arboretum, containing many fine specimens of 

 European and some -American trees. The arboretum 

 is rich in conifers, one, a cedar of Lebanon, being 

 unusually large and beautiful. A portion of the old 

 palace moat is maintained as a pond for aquatics. 

 The large palm house, the Victoria house, and other 

 greenhouses contain many interesting exotics. The 

 garden has also its special beds of poisonous, 

 economic and medicinal plants, as well as one con- 



Prof. E. Strasburger. From a photograph by K. Fujii. 



taining plants, widely separated in relationship, but 

 which have solved certain problems of adaptation ii> 

 the same way. But it is neither the laboratories, the 

 library, nor the botanic garden that has made the 

 institute at Bonn famous; rather the enthusiasm, 

 earnestness and profound resourcefulness of the master 

 mind that directs it. 



Prof. Strasburger began his notable series of in- 

 vestigations upon the conifers where Hofmeister left 

 off. In 1872 appeared the large volume with numerous 

 plates upon the morphology and fertilisation of coni- 

 fers and the Gnetaceae. This was followed in 1879 

 by another volume, dealing with the embryology of 

 gymnospenns and angiosperms. His attention having 

 been attracted by the nuclear figures in the endosperm 

 during his earlier studies on gvmnosperms, he soon 

 brought to publication a series of observations upon 

 nuclear and cell division. Just thirty-two years ago 

 the nucleus was traced in continuous sequence from 



