388 REV. GEORGE HENSLOW ON THE 
So, conversely, if self-fertilization is “injurious " for Ipomea, intercrossing is " injurious” 
for Pisum. 
We may, moreover, go further, and observe that a cross may actually infect a plant 
and bring about deleterious results; for Berkeley, while observing that “the main object 
to which the whole system of the organs in any individual plant tends is the reproduction 
of the species by means of seed," adds :—** The embryo partakes, not only of the nature 
of the plant which bears the seed, but, if the impregnation have taken place from the 
pollen of some neighbouring plant of the same species, of that of the male parent also. 
The seed, therefore, even of a healthy, much less of an unhealthy, plant will not neces- 
sarily produce a healthy offspring " *. 
Whichever way, however, we use the term *'injuriousness," it seems to be mis- 
leading, for it implies some positive evil instead of a mere relative degree of vigour; so 
I would prefer to suggest the term “ negative ” for both cases where no increased powers 
are acquired by the plant. 
The facts recorded by Mr. Darwin, and quoted in this section, appear to me to have great 
significance, and might be expressed by such an aphorism as permanently self-fertilized 
plants refuse to be intercrossed. Mr. Darwin, as we have seen, attributed this to the fact of 
their having been so long cultivated by self-fertilization under nearly the same conditions; 
but this would not seem to be any real explanation; and I find that Mr. Meehan has 
arrived at the same conclusion; for he says in a letter to me :— f 
33 
“ There is another matter which has occurred to me, but which I have not yet had time to work out 
to a positive conclusion ; those species which seed the most readily are self-fertilizers ; and they seem to 
abominate crossing. Disemma aurantiaca, an Australian species of Passifloracee, seeds with extreme 
freedom. I took care, as I thought, to keep all pollen from it but that of P, cerulea: I felt sure of a 
hybrid; but the result was only Disemma. At that time I thought I must have made a mistake, but I 
have since had the same experience with Primula japonica and P. involucrata; and my friend Parkman 
with Lilium auratum . . . . Why should “these cases only occur in instances where the plant seeds 
abundantly by its own pollen ? If cross-fertilization is a benefit, we should suppose that those which 
seeded the most freely would be in the most need of it, and show a greater See to receive outside 
aid when they could get it.” i 
Such is my view also, as ST above. 
15. Self-fertilized plants are perfectly healthy. 
Self-fertilized plants are, when in natural conditions, as healthy as intercrossed plan 
though exceptional cases may occur under cultivation. With regard to the first class, 
have but to remind the reader of the names of a few of the commonest and most troub je 
some “ weeds,” and he will doubtless have experienced their vigour and healthiness, suc 
as Groundsel, Sowthistle, Chickweed, Shepherd’s-purse, Knotweed, Buttereups, Solanum 
nigrum, species of Cerastium, Poa annua, Ee, Ee, all of which are highly and habitually 
self-fertile, and of which many propagate themselves with extraordinary rapidity, and 
are certainly far from warranting any belief in the injuriousness of self-fertilization. 
If we turn to Mr. Darwin’s pa several cases occurred where the self fertilized 
i * Yop: Ib? axir, $ 100 and aa $ 128, in‘ Gan. Cima? 1854 pp gon 3 
