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Show 304 'WEIGHT AND GERMINATION OF CRAP. IX. ness of stem."* Nor can this difference in the growth of the seedling turnips be attributed ~o the h~avic:· soecls having been of crossed, and the hgbter of s?lffertilisecl oriain for it is known tha.t plants belonging b ' b . to this genus are habitual]~ interc:·ossed y I~sec~s. With respect to the relative penod of germination ?f crossed and self-fertilised seeds, a record was kept In only twenty-one cases; and the .resul~s are very perplexing. Neglecting one ~ase In which the two lots germinated si1nultaneously, 111 ten. cases or. exactly o~ehalf many of the self-fertilised seeds germinated before the crossed, and in the other half many of the cro ·sed before the self-fertilised. In four out of these twenty eases, seeds derived fr0m a cross with a fresh stock were compared with self-fertilised seeds from o.ne. of the. later self-fertilised generations; and here again 1n half the cases the crossed seeds, and in the other half the self-fertilised seeds, germinated first. Yet the seedlings of Min1ulus raised from such self-fertilised seeds were inferior in all respects to the crossed seedlings, and in the case of Eschscholtzia they were inferior in fertility. Unfortunately the relative weight of the tw~ lots. of seeds was ascertained in only a few instances 1n whiCh their germination was observed; but with Ipomcca ~nd I believe with son1e of the other species, the relative lightness of the self-fertilised seeds apparently doter- * ' Gardeners' ClHonicle,' 18G7, p. 107. Loiseleur-Deslongchamp (' Les Cereales,' 1842, pp. 208-219) was led by his olJservations to · the extraordinary conclusion that tho smHller grains of cereals produce us fine plants as the large. 'fhi8 conclusion is, however, contradicted by Major Hallet's great success in im!Jroving wheat by the selection of the finest gminR. It is possible, however, that man, by long-continued sele~tion , ma~ have n-iven to the graws of the cereal~ a greater amount of starch or other mnttor, than the seedlinD'S can utilise for their growth. Th~re cR.n be littlo doubt, as Humbold.t long ago rcmarkell, that tile ()'rain~ of cereals l~;wu boen rend~red attractive to bn:ds in a degree which is highly mjurious to the species. CHAP. IX. CROSSED . AND SELF-FERTILISED SEEDS. 355 mined their ear!y germination, probably owing to the sma~ler mass beu~.g fa.vourable to the more rapid con1- pletion of the chemical and morphological chan o-es necessary for germination. On the other hand, lV[r. Galton gave me seeds. (no doubt all self-fertilised) of Lathyrus odorat~ts, which were divided into two lots of heavier and lighter seeds·; and several of the fonner ~erminated first. It is evident that many more observati? ns are necessary before anything can be decid d with respect to .the relative period of o-ermination of crossed and self-fertilised seeds. 0 2 A 2 |
