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Show 84 DIGIT,A.LIS PUBPUREA. CHAP. IlL TABLE XXIII. T l ll t Fl stem on each Plant measured: 0 means that tW ta es 1 ower-the Plant died before a Flower-stem was produced. No. of Pot. Crossed Plants. I Self-fertilised Plants. [ - lnr.hes. I Inches. I. 53~ I 27 ~ 57 a I 55 g 57 R 0 65 I 0 I .. ------ I 39 II. 34~ I 52~ 32 I 63~ 21 --- III. I 57 a 53 a I 53~ 0 I soB 0 37 § 0 IV. 64~ I 34~ s1a I 2 3~ .. 0 I --- v. I 53 I 0 47 * \ 0 I 34R 0 - Total in inches. I 821·25 ·I 287•00 The average height of tbe flower-stems of the sixteen cr?~sed plants is here 51· 33 inches; and that. of ~be eigb~ self-.ferbhsed plants, 35 · 87; or as 100 to 70. But this dlfi~re~ce In height does not give at all a fair idea of the vast superwnty of the crossed plants. These latter produced altogether sixty-four flower-stems, each plant producing, on an average, exactly four flower-s~ems; whereas the eight self-fertilised plants produced only fifteen flower-stems, each producing an average only of 1· 87 stems, a~d these bad a leRs luxuriant appearance. We may put the result Ill another way : the number of flower-stems on the crossed plants was to those on an equal number of self-fertilised plants as 100 to 48. Three crossed seeds in a state of germination were also planted in three separate pots; and three self-fertilised seeds in the same state in three other pots. · These plants were therefore at first exposed to no competition with one another, and when CHAP. III. CROSSED AND SELF-FERTILISED PLAN'rS. 85 turued out of their pots into the open ground they were planted at a moderate distance apart, so that they were exposed to much less severe competition than in the last case. The longest leaves on the ~hree crossed plants, when turned out, exceeded those on the self-fer~ilised plants by a mere trifle, viz., on an average by ·17 of an Inch. When fully grown the three crossed plants produced twenty-six flower-stems; the two tallest of which on each plant were on an average 54·04 inches in heio·ht. The three self-fertilised plants produced twenty-three flo;er-stems the two tallest of which on each plant had an average heiO'ht of 46 ·18 inches. So that the difference between these tw; lots which hardly competed together, is much less than in the last case when there was moderately severe competition, namely, as 100 to 85, instead of as 100 to 70. 'l'he .Effects on the Offspring of intercrossing d~fferent Plowers un the same Plant, instead of crossing disUnct Individuals.-A fine plant gro~ing in my gar?en (one of the foregoing seedlings) was covered With a net, and SIX flowers were crossed with pollen from · another flower on the same plant, and six others were fertilised with their own pollen. AU produced good capsules. The seeds from each were placed in separate watch-glasses, and no difference could be perceived by the eye between the two lots of seeds· a~d when they were weighed there was no difference of any sig~ mficance, as the seeds from the self-fertilised capsules weighed 7 · 65. grains, whilst those from the crossed capsules weighed !'7 grains. Therefore the sterility of the present species, when msects are excluded, is not due to the impotence of pollen on the stigma of the same flower. Both lots of seeds and seedlings were treated in exactly the same manner as in the previous table (XXIII.), excepting that after the pairs of germinating seeds had ?e.en planted on the opposite sides of eight pots, all the remammg seeds were thickly sown on the opposite sides of Pots IX. an~ X. in Table XXIV. The young plants during the following sprmg were turned out of their pots, without being disturbed and planted in the open ground in two rows, not very clos~ together, so that they were subjected to only moderately severe ~ompetition with one another. Very differently to what occurred m the first experiment, when the plants were subjected to somewhat severe mutual competition, an equal number on each side either died or did not produce flower-stems. The tallest flower-stems on the surviving plants were measured as shown in the following table :- ' |