HARDWICKE'S SCIENCE-GOSSIP. 



205 



vessels, which increase somewhat in size, from the 

 apex of the wedge outwards to the base. In young 

 specimens, the vessels are larger and more various in 

 size and form than is the case in more mature stems, 

 and the wedges are also more open. In older stems, 

 the vessels are smaller, and more regular in size, and 

 the exogenous zone is more firmly knit together, 

 which seem to have been effected by the growth of 

 new vessels and cells amongst the older ones, and 

 the formation of new wedges, in a regular exogenous 

 manner. The central medulla forms a solid pith, the 

 cells of which are generally largest in the centre, but 

 become smaller as they approach the woody wedges, 

 and fill up the spaces between them ; and being very 

 thin walled they give a very light appearance to the 

 pith, which forms a strong contrast to the darker 

 wedges of the ligneous zone, causing that star-like 

 appearance of the pith from which the plant derives 

 its name of Astromyelon. 



The Astromyelons differed also from Calamites in 

 their mode of branching. They had branches like 

 ordinary exogenous plants, while those of Calamites 

 were articulated to the stem, and were derived solely 

 from the bark. In the longitudinal sections of the 

 two plants a very striking difference is seen in the 

 form and structure of the pith, which is fistular (hollow 

 like a reed) in Calamites, with only a thin lining 

 enveloping the ends of the wedges, whereas in Astro- 

 myelon it forms a solid structure. In the latter plant 

 the pith extends continuously throughout the stem 

 and branches, but in Calamites it only forms a thin 

 lining round the chambers into which the stem of the 

 plant is divided. The structure of the pith is very 

 similar in the two plants. In the centre of Calamites 

 it partakes more of the character of a true parenchyma, 

 but in Astromyelon and between the wedges of Cala- 

 mites it is composed of long brick-like cells which 

 form a higher stage of cell structure, and it is known 

 under the name of parenchymatous tissue. The 

 beautiful regularity in which these long brick-like 

 cells are laid gives to longitudinal sections of the 

 pith the mural aspect which I have already alluded 

 to. This mural parenchyma, so commonly found in 

 modern exogenous plants, has been noticed by 

 Professor Williamson as forming a most conspicuous 

 feature in many of our fossil cryptoganiic plants. 



The Astromyelons may be divided into two great 

 groups, namely, the normal one, with the large star- 

 like pith, and another in which the pith is entirely 

 absent. There is such a striking difference between 

 these two forms, that were it not for the fact that I 

 have a large series of specimens showing a complete 

 gradation between them, they might be ranked as 

 two separate species. Some of my specimens have 

 the wedges clearly formed, but the pith has disap- 

 peared ; others show a continuous cylinder without 

 either wedges or pith. In both these cases it is very 

 probable that the pith has been lost, either during 

 the process of fossilisation or else before that process 



began. There are other cases which exhibit a 

 gradual enlargement of the woody cylinder at the 

 expense of the area of the pith, which gradually 

 becomes less and less, until we arrive at specimens 

 which present to our view a solid cylinder of woody 

 tissue, and with scarcely a trace of the medulla. It 

 will be seen from the above that the term Astromyelon 

 is not a very appropriate one to a large number of 

 specimens comprehended under that name, but this 

 is one of the inevitable consequences of the progress 

 of discovery. It is a common occurrence in geology 

 for names and even theories to be outgrown by the 

 accumulation of new facts. However incongruous it 

 may appear to some people to call plants which have 

 neither pith nor woody wedges, nor even the place 

 of the pith, by the name of " star-like pith," yet it is 

 better to do so than to introduce many new names, 

 which in course of time may become as inappropriate 

 as the one they supplant, and which will only tend tO' 

 perplex and hinder the student. By-and-by, when 

 our knowledge of the morphology and physiology of 

 these fossil plants becomes more perfect, these present 

 names, which are only provisional, will have to give 

 place to more appropriate ones. 



(7t7 be contirmed.) 



THE WILD FLOWERS OF 18S2. 

 By A. Kingston. 



THE remarkably mild winter and spring through 

 which we have passed have been so much the 

 subject of comment that the influence of this mild- 

 ness in promoting an unusually early maturity of 

 flowering plants can hardly be a matter for any great 

 surprise. Nevertheless, having made a definite record 

 of the earliest flowering period of a good number of 

 species observed in this (Royston) district, I have 

 thought that the extracts from such record which are 

 given below might not be altogether devoid of 

 interest: Chelidoiunni majus, April 17th; Reseda 

 liitea, end of May ; ffelianthemum viilgare, middle 

 of May ; Polygala vulgaris, April 17th; Stellaria 

 Holostea, March 25th j Arenaria serpyllifoUa, April 

 24th ; Cerasiiiim arz'ense, April 9th ; Lintim catkar- 

 ticitm. May 1st ; Ilyperieiim perforatum, June 20th ;. 

 Lotus cornictdatits, end of May ; Astragalus hypo- 

 glottis. May 15th ; Lathyrus pratensis, middle of 

 June^; Spiraa Filipendiila, June 1st ; Geuni zirhanuvi, 

 April ; Potentilla anserina, first week in May ; P.. 

 reptans, middle of May ; Rosa canina, middle of 

 May; Cratcrgtis Oxyacantha (" may "), occasionally 

 in sunny places last week in April ; Saiiicula 

 EuropcEa, middle of May ; Pimpinella saxifraga, in 

 May (solitary specimen) ; Daucus Carota, end of 

 May ; Scaiidix Pecten, in April j Sherardia arvensis, 

 in April ; Scabiosa Columbaria, end of May ; Crepis 

 virens, end of May ; Lapsana communis, June 1st j 



