4.12 SECTIONAL TRANSACTIONS.— K. 



(4) Female ' heads ' yielded the same insects, whose bodies and limbs were also 

 smeared with mucilage in which sperms were abundant. 



(5) The paraphyses surrounding the archegonia are well provided with mucilage 

 in which sperms were frequently seen actively motile. 



The mucilaginous contents of the paraphyses have obviously the primary function 

 of keeping the antheridia and archegonia moist, and secondarily, through the mediation 

 of insect visitors, of facilitating the transference of sperms from the male to the female 

 ' heads,' often at a considerable distance from the male ' heads.' Further investiga- 

 tions are being made, not only on other Musci but also on Hepaticae. 



27. Lecture by Prof. Sir Frederick Keeble, F.E.S., on Plant Inte- 



gration. 



Wednesday, Aiigust 11. 



28. Mr. M. A. H. TiNCKER. — The Effect of Length of Day upon the Growth 



and Internal Composition of some Economic Plants. 



The response in growth-habit of plants subjected to curtailed periods of daily 

 illumination has been described previously. Data now available indicate that this 

 treatment influences the composition of the tissues : — 



Dactylis glomerata — Cocksfoot ' Late Indigenous.' — •' lO-Hr. days ' prevent 

 flowering, cause reductions in the total dry weight per plant, in the percentage fibre 

 in leaf lamina and sheath ; higher percentages of ash, total nitrogen, and protein are 

 found in the leaves of treated plants. 



Phaseolus multiflorus — Runner bean. — ' 10-Hr. days ' accelerate flower production 

 and retard stem elongation. In the stem, whilst the percentage of dry matter is 

 increased, that of fibre is reduced. Much starch, however, is present. The dry 

 weight of the leaves and total dry weight of treated plants exceed that of the controls 

 at six weeks. The roots of treated plants are ' tuberised ' and contain much starch. 

 The leaves and stems of treated plants contain more protein than do controls. 



Helianthus tuherosus — Jerusalem artichoke. — ' 10-Hr. days ' limit stem elongation 

 but favour intense ' tuberisation.' The stems of treated plants contain much more 

 fibre and ash, the leaves less protein, than do control plants. Treated plants 

 accumulate most of their carbohydrate in tubers, controls (more elongated) in their 

 less fibrous stems. 



29. Prof. T. Johnson. — On Dipteris conjugatoides, n.sp. 



One of the least likely fossils to expect in the Irish flora is a representative of the 

 anomalous group of ferns — the DipteridincB — now confined to Malaya and Polynesia. 

 Dipteris, represented by four species, has occupied an isolated position in the Polypods, 

 and has also been regarded, with its incomplete more or less vertical annulus, as a 

 member of the AspidiecB. Fossil evidence, however, shows it to be the relic genus of 

 a group which had an almost world-wide distribution, in the Jurassic more especially. 

 Forms are recorded from Bohemia, not far from the locality in Moravia in which the 

 allied anomalous group Ilatoniacece occurred at the same time — the Upper Cretaceous. 

 But for fossil evidence Dipteris would still be regarded as an isolated Polypod. In 

 Camptopteris spiralis Nath. and other forms the group possesses some of the most 

 remarkable plants known. 



As the generic name indicates, the stipe of Dipteris may fork at its distal end so 

 that each prong carries one distinct half of the frond with its appropriate vascular 

 supply. The bifurcated or dichotomously divided lamina is itself palmately or 

 digitately lobed, the lobes being strap-shaped, ovate, &c., with entire or toothed 

 margin. Two main vascular bundles enter the lamina, one to each half from the 

 stalk, and these bundles themselves dichotomise five or six times in their passage 

 through the frond. The veins come off at a fairly definite angle, take a characteristic 

 curve, and may run side by side, more or less parallel to one another, in the same lobe. 

 The leaf may be so much segmented and the lobes so narrow that only one main 

 bundle runs through each lobe as a midrib. In such a case an isolated lobe would 

 not readily be recognised as part of a Dipteris frond. The smaller veins form a more 



