64 Mr. Darbishire. Experimental Estimation of the [Dec. 7, 



wings folded into their original position. The flower was then labelled. As a rule, I 

 pollinated four flowers with the pollen of a single flower, in order to save time. When 

 more than one flower has been pollinated from a single flower, this fact is indicated in 

 Tables I and II by writing all the crosses made with the pollen of a single flower on the 

 same line ; except in cases in which different kinds of pistil-parents were fertilised from 

 the same flower, when they are connected by a vertical bracket, as in crosses 121 — 124 

 (Table I). 



The flowers of the pistil-parent were not enclosed in bags after they had been pollinated. 

 I did not do this, because I had observed that bees did not visit the flowers until they 

 were open, i.e., a day or two after they had been pollinated. The neglect of this precau- 

 tion was justified by the event. With a single exception, all the crosses which "took" 

 proved successful, as could be determined in the autumn of the year in which the cross 

 was made in the case of G $ x Y $ , and in the following autumn in the case of Y ? xGiJ. 

 The exception referred to occurred in a cross between Wen-dou and a pure green — Express, 

 viz., cross No. 71 (Table II). When the pod containing the Fj cotyledons was opened, it 

 was found to contain four yellow and one green seed. This was presumably due to the 

 fact that the flower functioning as pistil-parent was operated on a little too late. 



All the crosses between the pure yellow and extracted green are recorded in Table I. 

 Those which gave no seed are indicated by being printed in italics. The date at 

 which the crosses were made is written against the first of the crosses made on a given 

 date. Table II is a list of the (successful) control crosses, to be described later on (p. 69). 



Tables III to VI give the numbers of yellows and greens in individual families com- 

 posing F 2 from the cross between the yellow and the extracted green, and a summary of 

 all the families composing this F 2 is given after Table VI. Tables VII and VIII give 

 details of F„ from the control crosses. When there was any doubt as to the colour of a 

 seed, it was recorded as doubtful. The number of such seeds, if they occur, in each family* 

 is given in the column headed with a ?. The families of F 2 cotyledons from the cross 

 between the pure yellow and the extracted green are given in two lots, in one of which 

 (Tables III, IV, and V) it has been possible to classify the families according to the green 

 and also according to the yellow parent forms from which they have sprung, and in the 

 other of which (Table VI) this classification has not been possible, owing to an accident. 

 This occurred during harvesting. The plant or plants bearing the F 2 families from 

 cross 166 were accidentally incorporated in a bundle with the plants from some other 

 cross. I discovered this by finding the peg with 166 on it, after the day's harvesting, 

 rather deep in the ground (the top was just covered), as I was hoeing. So that, knowing 

 the mistake had occurred that day, I was able to know in which bundles 166 had been 

 incorporated. If I had kept a record of the number of seeds I sowed from each cross, I 

 should have been able to discover the plants bearing the F 2 from cross 166 during the 

 process of recording ; but I had not done this, in these particular sowings, partly because 

 the ground had not been used for peas before (not in itself a sufficient justification), and 

 partly because the seeds containing the F 1 cotyledons had been sown exactly 9 inches 

 apart, so that if stray seeds did come up, they could not escape detection. (The rows were 

 carefully examined during the process of weeding, which was done with great minute- 

 ness with the hand, the smallest seedlings being removed). t The families of F 2 cotyledons 

 which cannot, as a result of this accident, be classified according to their yellow and 

 green parent forms, have been given under a separate heading ; but it must be under- 

 stood that one of them (which, there is no means of discovering) contained an additional 



* By " family " I mean, in the present case, the number of peas on a plant, 

 t I have reorganised the method of carrying out my experiments in such a way that no 

 further mistakes of this kind can occur. 



