410 SECTIONAL TRANSACTIONS.— K. 



chromosomal irregularities to be of very frequent occurrence in the fatuoids. Specific 

 irregularities are also correlated with an unusual segregation ratio in one strain of 

 heterozygous fatuoids. Extremely irregular cytological conditions are characteristic 

 of the sterile dwarf fatuoids, which occur commonly in some strains and only 

 occasionally in others. The combined genetical and cytological evidence obtained 

 in these studies indicates that fatuoids owe their origin to chromosomal aberrations. 



21. Miss C. Clint. — The Life-history and Cytology of Sphacelaria Cirrhosa, 



var. Aegrophila. 



The paper deals with the relationship of Sphacelaria to its host-plant, Halidrys 

 siliquosa, and traces the distribution of the former over a considerable area of coast, 

 and its development throughout a twelve-month period. 



The cytology has been worked out and the position of the reduction-division in 

 the life-cycle established. Special attention has been paid to the nature and behaviour 

 of the spores from two types of sporangia ; sexuality has been definitely established 

 in one of them. 



Tuesday, August 10. 



22. Miss S. H. Maktin, Miss M. W. Kea, and Prof. J. Small. — The 



Reaction of Plant Tissues. 



Method. — By using a series of indicators upon fresh-washed sections and noting 

 colours rather than tints, the reaction may be placed definitely within one of a series 

 of ranges. 



Results. — A preHminary survey of 166 species, using in most cases the young 

 flowering stem, shows : (I) that the tissue reactions vary in general between PjjB.O 

 and Pjj4.0, and (2) that certain tissues, e.g. xylem and epidermis, tend to be more 

 acid than others, e.g. cortex. Tendencies towards greater or lesser acidities are 

 indicated in particular families or groups of families. 



Detailed studies of the reaction of all tissues of the sunflower and the broad-bean, 

 from the seed stage to anthesis, indicate that, while the reaction of some tissues remains 

 constant, that of others varies with position above or below soil and with age. 



The buffer action in the sap from the hypocotyl of the sunflower is shown to be 

 due to a very dilute solution of inorganic phosphates. 



Other results include the tissue reaction of selected stems for each month of the 

 year and of the stems and leaves of a few species in a variety of habitats. 



23. Miss Fry. — The Penetration of Lichen Gonidia by Fwigal Constituents, 



with special reference to Lecania candicans, 



24. Joint Discussion with Sections C {q.v.) and D on The Conception 



of a Species. 



25. Joint Meeting with Sub-section K* {q.v.). Prof. J. W. Bews. — 



The Ecological Evolution of Angiospermous Woody Plants. 



26. Dr. E. Krausel. — On New Devonian Plants. 



The flora of the Middle Devonian of Elberfeld consists of a series of plants, which 

 are evidently from different sources. Some of them are autochthonous ; they grew 

 in rush-like clumps in a shallow coastal lagoon. On the other hand, water- transported 

 remains of land-plants are also present. 



Among the lagoon- plants occurs, first of all, a tall-growing Asteroxylon, A. elber- 

 feldense, of which the upper, naked sporangiophores were first described as Hostimella 

 hostimensis.^ 



1 It appears, however, that the Bohemian Hostimellas belong rather to Pseudo- 

 sporochnus. This genus is a true member of the PsUophytaoese, for the supposed 

 ' leaves ' are nothing but the terminal sporangia. Some badly preserved fragments 

 from Elberfeld may belong to Pseudosporochnus. 



