MENDEL 



inflated, not contracted in places; or 

 they are deeply constricted between 

 the seeds and more or less wrinkled 

 (P. sac char atimi) . 



5. To the dijference m the colour of 

 the imripe pods. They are either light 

 to dark green, or vividly yellow,, in 

 which colouring the stalks, leaf-veins, 

 and calyx participate.* 



6. To the difference in the position 

 of the flowers. They are either axial, 

 that is, distributed along the main 

 stem; or they are terminal, that is, 

 bunched at the top of the stem and 

 arranged almost in a false umbel; in 

 this case the upper part of the stem 

 is more or less widened in section (F. 

 imibellatimi) .-^ 



1 . To the difference in the length of 

 the stem. The length of the stem ^ is 

 very various in some forms; it is, how- 

 ever, a constant character for each, in 

 so far that healthy plants, grown in the 

 same soil, are only subject to unimpor- 

 tant variations in this character. 



In experiments with this character, 

 in order to be able to discriminate with 

 certainty, the long axis of 6 to 7 ft. was 

 always crossed with the short one of 

 % ft. to 1 Vi ft. 



Each two of the differentiating 

 characters enumerated above were 

 united by cross-fertilisation. There 

 were made for the 



4 One species possesses a beautifully 

 brownish-red coloured pod, which when 

 ripening turns to violet and blue. Trials with 

 this character were only begun last year. [Of 

 these further experiments it seems no account 

 was published. Correns has since worked 

 with such a variety.! 



^ [This is often called the Mummy Pea. It 

 shows slight fasciation. The form I know has 

 white standard and salmon-red wings.] 



* [In my account of these experiments 

 (R.H.S. Journal, vol. xxv. p. 54) I misunder- 

 stood this paragraph and took "axis" to mean 

 the floral axis, instead of the main axis of the 

 plant. The unit of measurement, being indi- 

 cated in the original by a dash ('), I care- 

 lessly took to have been an inch, but the 

 translation here given is evidently correct.] 



1st trial 60 fertilisations on 15 plants. 



From a larger number of plants of 

 the same variety only the most vigor- 

 ous were chosen for fertilisation. 

 Weakly plants always afford uncertain 

 results, because even in the first gen- 

 eration of hybrids, and still more so 

 in the subsequent ones, many of the 

 offspring either entirely fail to flower 

 or only form a few and inferior seeds. 



Furthermore, in all the experiments 

 reciprocal crossings were effected in 

 such a way that each of the two vari- 

 eties which in one set of fertilisation 

 served as seed-bearer in the other set 

 was used as the pollen plant. 



The plants were grown in garden 

 beds, a few also in pots, and were 

 maintained in their naturally upright 

 position by means of sticks, branches 

 of trees, and strings stretched between. 

 For each experiment a number of pot 

 plants were placed during the bloom- 

 ing period in a greenhouse, to serve 

 as control plants for the main experi- 

 ment in the open as regards possible 

 disturbance by insects. Among the in- 

 sects "^ which visit Peas the beetle 

 Brjichus pisi might be detrimental to 

 the experiments should it appear in 

 numbers. The female of this species is 

 known to lay the eggs in the flower, 

 and in so doing opens the keel; upon 

 the tarsi of one specimen, w^hich was 

 caught in a flower, some pollen grains 

 could clearly be seen under a lens. 

 Mention must also be made of a cir- 

 cumstance which possibly might lead 



7 [It is somewhat surprising that no men- 

 tion is made of Thrips, which swarm in Pea 

 flowers. I had come to the conclusion that 

 this is a real source of error and I see Laxton 

 held the same opinion.] 



