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JOURNAL OF THE KOYAL HORTICULTURAL SOCIETY. 



the case before us it cannot be immaterial what plants are subjected to 

 experiment and in what manner such experiments are conducted. 



The selection of the plant group which shall serve for experiments 

 of this class must be made with all possible care if it be desired to avoid 

 at the outset every risk of questionable results. 



The trial plants must necessarily — 



1. Possess constant differentiating characters. 



2. The hybrids of such plants must, during the flowering period, be 

 protected from the influence of all foreign pollen, or be easily capable of 

 such protection. 



The hybrids and their offspring should suffer no marked disturbance 

 in their fertility in the successive generations. 



Accidental impregnation by foreign pollen, if such occurred during 

 the experiments and were not recognised, would lead to entirely erroneous 

 conclusions. Reduced fertility or entire sterility of certain forms, such 

 as occurs in the offspring of many hybrids, would render the trials very 

 difficult or entirely frustrate them. In order to discover the relations in 

 which the hybrid forms stand towards each other and also towards their 

 j)rogenitors it appears to be necessary that all members of the series 

 developed in each successive generation should be, without exception ^ 

 subjected to observation. 



At the very outset special attention was devoted to the Leguminosce 

 on account of their peculiar floral structure. Experiments which were made 

 with several members of this family led to the result that the genus PisuiiL 

 was found to possess the necessary conditions. 



Some thoroughly distinct forms of this genus possess characters 

 which are constant, and easily and certainly recognisable, and when their 

 hybrids are mutually crossed they yield perfectly fertile progeny. Further- 

 more, a disturbance through foreign pollen cannot easily occur, since the 

 fertilising organs are closely packed within the keel and the anther 

 bursts within the bud, so that the stigma becomes covered with pollen 

 even before the flower opens. This circumstance is of especial importance. 

 As additional advantages worth mentioning, there may be cited the easy 

 culture of these plants in the open ground and in pots, and also their rela- 

 tively short period of growth. Artificial fertilisation is certainly a somewhat 

 elaborate process, but nearly always succeeds. For this purpose the bud 

 is opened before it is perfectly developed, the keel is removed, and each 

 stamen carefully extracted by means of forceps, after which the stigma can 

 at once be dusted over with the foreign pollen. 



In all, thirty-four more or less different varieties of Peas were obtained 

 from several seedsmen and subjected to a two years' trial. In the case of 

 one variety there were remarked, among a larger number of plants all alike, 

 a few forms which were markedly different. These, however, did not vary 

 in the following year, and agreed entirely with another variety obtained 

 from the same seedsmen ; the seeds were therefore doubtless merely acci- 

 dentally mixed. All the other varieties yielded perfectly constant and 

 similar offspring ; at any rate, no essential difference was observed during 

 the two trial years. For fertilisation twenty-two of these were selected 

 and cultivated during the whole period of the experiments. They remained 

 constant without any exception. 



