SECTIONAL TRANSACTIONS.— K. 397 



as a synonym. This affords evidence for supposing that the Beacon Sandstone 

 is of an Upper Triassic or Rhaetic horizon. 



7. Dr. H. S. HoLDEN and Miss Dorothy Bexon. — On the Seedling 



Structure of Acer p^^cudoplatdnun. 



The embryo of the sycamore, at the time the fruits are shed, consists 

 entirely of parenchyma, the vascular structures being represented by desmogen 

 strands. It contains abundant food reserves, consisting of : (a) starch, which 

 is uniformly distributed through the tissues, (l>) proteins, of which there are 

 at least two, existing in colloidal solution. 



In spring the proto.xylem and first metaxylem elements are differentiated 

 prior to germination. Each cotyledon is traversed by a midrib, with a stout 

 lateral and a smaller marginal bundle on either side. At the base of the 

 cotyledon the metaxylem of the midrib separates into lateral groups, which 

 unite with the converging laterals and marginals, so that four massive bundle? 

 in the diagonal position enter the hypocotyl with isolated protoxylems in the 

 cotyledonary plane. These ultimately give rise to a tetrarch root. 



The histology of the xylem in the hypocotyl and young epicotyl shows that 

 the component elements exhibit a relatively wide variation in type of pitting 

 and other characters which may provide phyletic data. 



8. Miss T. L. Prankerd and Miss F. M. 0. Waight.— On the Pre- 



sentation Time and Lateyit Time for Reaction to Gravity in 

 Pteridophytes. 



The object of the present work is to express quantitatively some of the facts 

 of irritability already described for fern fronds {P.h'.S., B.. 93, 1922). An 

 attempt has already been made to measure the intensity of gravitational 

 irritability in the fronds of Asplenium hulbiferum by finding the presentation 

 time, which is shown to vary greatly with the age of the frond, the temperature, 

 and possibly with some other factors. At 20° C. the range for presentation 

 time is at least 8 hours — ^ hour, and for the corresponding latent period 

 16 — 4 hours, the latter thus bearing an increasing ratio to the former. 



Effect of temperature on presentation and latent time. Connection with 

 growth and nutation. Comparison of results with those obtained for other 

 plants. 



9. Dr. W. L. Balls.— T/!P Groivth Structure of a CeU-Wall. 

 Published observations on the structure of the epidermal seed hairs of the 



cotton plant have shown that the secondary cellulose of the wall may consist of 

 a number of concentric growth-rings, deposited centripetally, one each day ; 

 further, that through these growth-rings runs a radial structure, or even two 

 such structures, visible to some extent in the natural state, but more clearly 

 defined after appropriate treatment. Thus, each growth-ring consists of a 

 number of spiral fibrils, the direction of the spirals frequently reversing. The 

 primary spiral pattern for any one hair appears to be laid down in the primary 

 wall during growth in length, and thereby to pre-determine the same pattern 

 for all the succeeding growth-rings of the secondary wall. 



Incidental observations suggest that this kind of structure is not peculiar 

 to cotton. Various points of interest arise with respect to the composition of 

 cellulose, the mechanism of growth, inhibiting factors, the development of 

 form, and a possible geometric structure in the cell. Generally, the observa- 

 tions suggest that it may be practicable to attack growth problems from the 

 sub-microscopic side. 



10. Prof. A. H. Eegixald Buller. — Tlie Organisation of the 



Hymeniu7n of the Common Mushroom and its Allies for the 



Production and Liberation of Spores. 



The author, using a new method of investigation, has succeeded in elucidating 



the time and space relations of the elements making up the hymenium in the 



common mushroom and its allies. 



The gills of Psatliota cnmprxfris are finely mottled, and the mottling is of 

 the same nature as that of Pa/uvolus campanulatiis. The basidia of the darker 



