SECTIONAL TRANSACTIONS.— K. 403 



To test this supposition reciprocal crosses were made with the two varieties, plants 

 being used which had been seKed for several generations and proved to breed true to 

 type. The seedlings from the outset showed a considerable difference. All those 

 derived from crossing the petaloid form with pollen of the apetalous variety had 

 dissected leaves, while those resulting from the apetalous form pollinated with pollen 

 from the petaloid variety had almost undivided leaves. There was thus a marked 

 contrast in the reciprocal crosses. 



The offspring with divided leaves all bore flowers with distinct petals, but the 

 number of the latter showed considerable variation, the average number being three 

 or four, with a variation from one to five. In no case were thej' apetalous. These 

 would therefore represent the forms occasionally found in Nature. 



On the other hand, the offspring derived from the reciprocal cross showed no inter- 

 mediate condition, but were, with one exception, all apetalous and exactly like the 

 female parent. As there seemed a possibility that this striking occurrence might be 

 due to apogamous reproduction, castrated plants were left unpollinated, but no seed- 

 production took place. Two further generations have been bred from these crosses, 

 but the plants continued to bear apetalous flowers and leaves with very slight incisions 

 exactly like the female parent from which they have sprung. 



This crossing therefore seems to result in what Blaringhem calls ' unilateral inherit- 

 ■ance,' similar to the results obtained by Gaertner in the case of Lychnis flos cuculi, 

 by MUlardet with various species of Fragaria (fausses hybrides), and by GriUer in his 

 •crosses of Vilis and Ampelopsis. 



6. Prof. J. Percival. — Aegihps x Wheat Hybrids. 



The author has obtained hybrids of Aegilops ovata with the wheats Wild Emmer 

 {Triticum dicoccoides), Emmer {T. dicoccum), Macaroni Wheat {T. durum), and Bread 

 Wheat [T. vulgare), the Aegilops being the mother planO. In almost all morphological 

 characters the hybrids were intermediate between the two parents. Reciprocal 

 crosses were unsuccessful. 



Meiosis and pollen formation in the hybrids ^. ovata x T. dicoccum and .4. ovata x 

 T. vulgare have been studied. 



Afternoon. 

 Excursion to Swinford Bridge (to study aquatic plants). 



Friday, August 6. 



7. Prof. H. H. Dixon, F.R.S., and Mr. T. A. Bennet-Clark.— 



Electrical Stimulation and Response in Plant Tissues. 



The passage of a current through a tissue leads to a change of electrical resistance 

 and to a change of permeability. The relationship between change in resistance and 

 the intensity and duration of the current has been examined. ' Very small ' stimuli 

 cause an increase in resistance, ' larger ' stimuli cause a decrease. There is a definite 

 period of development of the maximum effect, followed by a recovery. The same 

 quantity of electrical energy is found to be the more effective the higher the potential 

 At which it is applied. The change in resistance in different regions and in different 

 directions in the tissue, the effects of a second stimulus on tissue already stimulated, 

 also temperature and seasonal effects on resistance and on sensitivity, have been 

 investigated. 



8. Dr. Malcolm "Wilson and Miss E. J. Cadman. — Recent work on 



Reticularia and other Mycetozoa, and its Bearing on the Position 

 and Classification of the Group. 



In Reticularia lycoperdon there is no definite myamceboid stage. The fusion 

 takes place between gametes which are identical with the swarm-cells. Before the 

 fusion of the gametic nuclei the zygote coalesces with a number of swarm-cells, the 

 nuclei of which usually undergo direct division and are ultimately digested. Later 

 ingestion of entire swarm-cells may take place. The fusion nucleus in the young 



