404 SECTIONAL TRANSACTIONS.— K. 



The buffer conditions in the extracted sap are not identical with the conditions 

 ■which obtain in the intact tissues, for soluble calcium and soluble phosphates are more 

 or less sharply segregated from each other in the tissues. 



Miss L. E. Hawker. — A Quantitative Study of the Geotropism of certain 

 Seedlings, with special reference to the Nature and Development of their 

 Statolith Apparatus. 



Seedlings of about 80 different species selected from the Dicotyledons, Monocotyle- 

 dons and Gymnosperms have been examined in order to give a general review of the 

 morphology of the statolith apparatus from its first appearance in the seedling to its 

 establishment in the young plant. 



An attempt has been made to determine quantitatively the amount of statenchyma 

 present at different stages in the development of seedlings of each of the three groups. 



The presentation times for gravity have been measured for different periods in the 

 development of the seedlings in about 15 representative species, and the lowest of 

 these in each case, i.e. the maximum sensitivity to gravity, shows an interesting 

 correlation with the maximum amount of statolith starch present, which is in accordance 

 with the statolith theory. 



A suggested explanation is offered of the phenomenon of physiological zygomorphy 

 in the light of the statolith theory. 



Afternoon. 

 Prof. R. R. Gates. — Haploid Plants. 



A haploid Oenothera rubricalyx appeared in a culture of Oe.rubricalyx X eriensis in 

 1929, the remaining plants being true hybrids of a non-viable type. The haploid egg 

 cell of rubricalyx w^as probably induced to develop parthenogenetically by the presence 

 of pollen tubes belonging to a distantly related species. The haploid plant was a 

 slender dwarf with narrow leaves, and totally sterile. Its cells and nuclei are smaller 

 than the type. Other recent cases of haploid flowering plants are discussed. They 

 have occurred in Datura, Nicotiana, Solanum, Triticum, Matthiola, Oenothera and 

 Crepis, and may apparently result from the entrance of foreign pollen tubes or from the 

 stimulus of low temperature acting on the egg, or occasionally they may occur 

 ' spontaneously.' Cases of haploid merogony are also recorded in Nicotiana and 

 other genera. 



The occurrence of haploid sporophytes having the same general morphologj' as the 

 diploid shows that one set of chromosomes is sufficient to produce the sporophyte. 

 This appears to be contrary to the former antithetic theory of the sporophyte as 

 a post-sexual phase intercalated between two gametophytes. 



Prof. J. Walton. — A Fossil Hollow Tree of Lower Carboniferous Age and 

 its Contents. 



In 1865 Wunsch recorded the occurrence of petrified Lepidodendroid trees in beds 

 of volcanic ash on the north-eastern shore of Arran in the Firth of Clyde. Carruthers, 

 Binney, and WiUiamson have examined and described various plant fossils from these 

 beds. A re -examination of some of the large blocks of these trees at present in the 

 Manchester Museum, by means of peel-sections, shows that before fossilisation had 

 occurred the trees had partly decayed, and all that remained was a hollow shell of 

 bark which had become filled with a varied collectionof plant fragments from outside. 



In two specimens, one at Manchester, the other at Cambridge, there appear to be 

 four or five steles in each hollow trunk. It seems probable that they represent 

 fragments of the single stele which broke into fragments when the soft surrounding 

 tissues decayed, and fell down side by side into the base of the stump. Some of 

 these fragments are penetrated by Stigmarian rootlets. Several Stigmarian axes, as 

 well as the roots of other kinds of plants, indicate clearly that there were plants 

 growing at a higher level which sent their roots down into the hollow trunk. Among 

 the more frequent plant remains in the stumps are petioles of a Lyginorachis closely 

 allied to Lyginorachis papilio Kidston, .Protocalumites, Lepidocarpon, and .several 

 types of Lepidodendroid stems. 





