(JCTOBER. 1911. 



KNOWLEDGE. 



403 



VAKI.ABLE ST.AKS.— Mr. Joel Stebbins, who lately 

 detected the secondary niinimuin of Algol with the selenium 

 photometer, has detected a small variation of light in i^ 

 .•\urigae, a spectroscopic binary, showing that each star 

 partially eclipses the other in the course of a revolution. The 

 radius of each component is deduced as 2-6 that of the sun, 

 the mass of each two and one-third that of the sun. and 

 density one-third of his. Assuming a parallax of 0"-0J. each 

 component gives eighty times as much light as the sun at 

 the same distance, while their intrinsic surface brightness is 

 twelve times his. According to the diagram given, about one 

 (luarter of the diameter of each star is covered by the other 

 at mid-eclipse. Mr. Stebbins has also discovered variability 

 in 5 Orionis, but his discussion on this is not yet complete. 

 He proposes to e.xamine other spectroscopic binaries, as, 

 owing to their close pro.ximity. partial eclipses must occur 

 in a considerable proportion of them L-Xsfropliys. Joitrn., 

 September). 



Dr. Ejner Hertzsprung {Astr. Xaclir. 451iSl has detected a 

 variation in Polaris of 0- 17 magnitude in a period j-96Sl days, 

 the same as that of its orbital motion given by the spectroscope. 

 This is not, however, considered to belong to the Algol but to 

 the Cepheid class, the variation being due to the difi'erent 

 presentations of an elong.ited spheroid. 



BOTANY. 



By Professor F. C.weks, D.Sc, F.L.S. 



BOTANY AT THE HKITISH ASSOCIATION.— The 

 meetings of Section K (Botany I at Portsmouth this year were 

 of unusual interest owing to the presence of a large contingent 

 of Continental and .American botanists. During the four 

 weeks preceding the commencement of the Portsmouth meet- 

 ing these distinguished visitors, along with a number of 

 British botanists, had made an extensive tour of this country, 

 specially arranged for them by the International Phyto- 

 geographical Excursion Committee. 



.\s might have been expected in the circumstances, l-^colugy 

 formed an outstanding feature of the meetings, perhaps to the 

 exclusion of other departments of Botany, so that the papers 

 read were not quite so representative as usual of the science 

 as a whole. Two entire days were devoted to Ecology, and 

 several ecological papers were also given on the other days. 



PRESIDENT! AL ADDRESS.— In his Presidential Address 

 to the Section, Professor F. E. Weiss, of Manchester Univer- 

 sity, devoted himself mainly to the consideration of certain 

 problems in Fossil Botany, not omitting that attractive phase 

 of the subject, the Ecology of fossil plants. He pointed out 

 that the possibilities of vegetable fossils preserved only as 

 inipressioits in the rocks had been practically exhausted in 

 1870, when Sachs published his fascinating History of Botany, 

 and dwelt upon the debt which botanists owe to the pioneers 

 of modern Palaeobotany — Binney, Williamson, Renault, and 

 others — who first show-ed that the structure of fossil plants is 

 in certain cases preserved in the most remarkable manner by 

 petrifaction and can be studied in microscopic preparations as 

 effectively as has been the case with recent plants since the 

 days of Grew and Malpighi. 



After dealing with the (luestion of the homology of the well- 

 known Stigiuaria, and reviewing the various explanations that 

 have been put forward regarding the nature of the Stigmarian 

 axis and its appendages. Professor Weiss concluded that 

 various recent observations strongly support Williamson's 

 view that Stigniaria was a down-growing prolongation of the 

 stem of the Lcpitlodeitdron and Sigillaria to which it 

 belonged, corresponding to the lower part of the stem of the 

 present-day plant Isoi'tcs, the Stigmarian appendages answer- 

 ing to the roots given off by this portion of the plant in Isoctcs. 

 Apparently the one thing now lacking to complete the chain of 

 evidence in favour of Williamson's theory is the discovery of 

 tips of Stigiuaria rootlets showing structure. 



Passing onto the remarkable Pteridosperms, which combine 



the characters of Ferns and Cycads, Professor Weiss called 

 attention to the criticisms which Chodat has recently put 

 forward a.gainst the too wholesale acceptance of the view that 

 these seed-bearing, yet fern-like, plants form the " missing 

 link" between Ferns and Cycads. .According to Chodat the 

 stem of a typical Pteridosperm like Lyginudendrou presents 

 purely fern-like characters in its structure, contending that the 

 bundles of primary wood are not " mesarch," like the leaf- 

 bundles of C\-cads, but have only centrifugal wood ; while the 

 presence of secondary growth in thickness is no indication of 

 Cycad affinity, but is merely comparable to what is found in 

 various other fossil Ferns and Fern-allies. Chodat regards the 

 "seed" of Lyginodcndron as being merely a specialised 

 development of the megaspore, corresponding to the seed-like 

 organ found in the extinct Lycopod genus Lepidocarpon, and 

 considers that the origin and the biology of this kind of ""seed" 

 must have been \ery difterent from those of the seeds of the 

 Gymnosperms. In bringing forward Chodat's views, which 

 run counter to those generally accepted in this country, 

 on the nature of the Pteridosperms as the result of the brilliant 

 discoveries of Oliver and Scott, Professor Weiss disclaimed 

 any desire to urge their acceptance, but considered that 

 Chodat's criticisms are sufficiently weighty to demand careful 

 reinvestigation of the structure of some of the Pteridosperms, 



Professor Weiss proceeded to make some criticisms of his 

 own regarding recent theories on the origin of the .^ngiospernis 

 from the Meso^oic group Bennettitales, pointing out that some 

 botanists have " exceeded the speed-limit " in too rapid 

 formulation and acceptance of such theories, and expressing 

 his desire " to walk circumspectly in the very alluring paths 

 by which they have sought to explore the primaeval forest, 

 and not to emulate those rapid but hazardous flights which 

 have become so fashionable of late." 



In the latter part of his address, Professor Weiss dealt with 

 the biology and ecology of fossil plants, a wide and promising 

 field of research, of w hich only the fringe has yet been touched. 

 Since the remains of plants are sometimes continuous through 

 adjacent coal-balls ("calcareous nodules"! it is clear that 

 these concretions were mainly formed (';; situ, and that the 

 plant remains they contain represent samples of the vegetable 

 debris of which the coal-seam consists, giving us an epitome 

 of the vegetation existing in Palaeozoic times on the area 

 occupied by the coal-seam; while the Stigmarian rootlets in 

 the underclay help to prove that the seam usually represents 

 the remains of the Coal Measure forest carbonised //( situ. 

 This raises the question : What were the physical and climatic 

 conditions of these primaeval forests ? The structure of the 

 roots of Calamites. Lepidodendra. and so on, with their large 

 air-spaces, leads us to believe that, like many of their existing 

 relatives, these plants were rooted under water or in water- 

 logged soil ; while the narrowness and the xerophilous 

 structure of the leaves of these plants closely resembles the 

 modifications met with in our marsh plants. None of the 

 living Equisetales or Lycopodiales — the groups to which 

 belong the Cal.amites, Lepidodendrons. and Sigillarias of the 

 Coal Period — grow in salt marshes. Nor is it necessary to 

 invoke the salinity of the marsh to explain the good preserva- 

 tion of the tissues of the plant remains, in \'iew of the well- 

 known power of humic substances to retard decay of vegetable 

 tissues. Again, certain fungi found as parasites in coal 

 plants seem to support the fresh-water nature of the swamp, 

 just as the occurrence of a mycorhiza or " fungus servant " 

 in some coal plants seems to indicate the presence of a peaty 

 substratum. In some cases, millipedes and fresh-water shells 

 occur in the Coal Measures among the plants ; and the possible 

 presence of marine organisms may be accounted for by 

 occasional invasions of the Coal Measure swamps by the sea, 

 especially as these swamps may well have been estuarine or 

 formed near the sea. 



Since so many types of vegetation are found in the Coal 

 Measures, it is somewhat difficult to explain the occurrence, 

 side by side, of land-plants and marsh-plants, though in certain 

 cases it is clear that the remains of land-plants were carried 

 into the swamp after its submergence below the sea. However, 

 we can at the present day trace the gradual development of a 



