Volume Ii Part 34 (2/2)
2.XI.I. MISCELLANEOUS, 1863-1866.
LETTER 658. TO D. OLIVER. Down [April, 1863].
(658/1. The following letter ill.u.s.trates the truth of Sir W.
Thiselton-Dyer's remark that Darwin was never ”afraid of his facts.”
(658/2. ”Charles Darwin” (Nature Series), 1882, page 43.) The entrance of pollen-tubes into the nucellus by the chalaza, instead of through the micropyle, was first fully demonstrated by Treub in his paper ”Sur les Casuarinees et leur place dans le Systeme naturel,” published in the ”Ann. Jard. Bot. Buitenzorg,” X., 1891. Two years later Miss Benson gave an account of a similar phenomenon in certain Amentiferae (”Trans. Linn.
Soc.” 1888-94, page 409). This chalazogamic method of fertilisation has since been recognised in other flowering plants, but not, so far as we are aware, in the genus Primula.)
It is a shame to trouble [you], but will you tell me whether the ovule of Primula is ”anatropal,” nearly as figured by Gray, page 123, ”Lessons in Botany,” or rather more tending to ”amphitropal”? I never looked at such a point before. Why I am curious to know is because I put pollen into the ovarium of monstrous primroses, and now, after sixteen days, and not before (the length of time agrees with slowness of natural impregnation), I find abundance of pollen-tubes emitted, which cling firmly to the ovules, and, I think I may confidently state, penetrate the ovule. But here is an odd thing: they never once enter at (what I suppose to be) the ”orifice,” but generally at the chalaza...Do you know how pollen-tubes go naturally in Primula? Do they run down walls of ovarium, and then turn up the placenta, and so debouch near the ”orifices” of the ovules?
If you thought it worth while to examine ovules, I would see if there are more monstrous flowers, and put pollen into the ovarium, and send you the flowers in fourteen or fifteen days afterwards. But it is rather troublesome. I would not do it unless you cared to examine the ovules.
Like a foolish and idle man, I have wasted a whole morning over them...
In two ovules there was an odd appearance, as if the outer coat of ovule at the chalaza end (if I understand the ovule) had naturally opened or withered where most of the pollen-tubes seemed to penetrate, which made me at first think this was a widely open foramen. I wonder whether the ovules could be thus fertilised?
LETTER 659. TO D. OLIVER. Down [April, 1863].
Many thanks about the Primula. I see that I was pretty right about the ovules. I have been thinking that the apparent opening at the chalaza end must have been withering or perhaps gnawing by some very minute insects, as the ovarium is open at the upper end. If I have time I will have another look at pollen-tubes, as, from what you say, they ought to find their way to the micropyle. But ovules to me are far more troublesome to dissect than animal tissue; they are so soft, and muddy the water.
LETTER 660. TO MAXWELL MASTERS. Down, April 6th [1863].
I have been very glad to read your paper on Peloria. (660/1. ”On the Existence of Two Forms of Peloria.” ”Natural History Review,” April, 1863, page 258.) For the mere chance of the following case being new I send it. A plant which I purchased as Corydalis tuberosa has, as you know, one nectary--short, white, and without nectar; the pistil is bowed towards the true nectary; and the hood formed by the inner petals slips off towards the opposite side (all adaptations to insect agency, like many other pretty ones in this family). Now on my plants there are several flowers (the fertility of which I will observe) with both nectaries equal and purple and secreting nectar; the pistil is straight, and the hood slips off either way. In short, these flowers have the exact structure of Dielytra and Adlumia. Seeing this, I must look at the case as one of reversion; though it is one of the spreading of irregularity to two sides.
As columbine [Aquilegia] has all petals, etc., irregular, and as monkshood [Aconitum] has two petals irregular, may not the case given by Seringe, and referred to [by] you (660/2. ”Seringe describes and figures a flower [of Aconitum] wherein all the sepals were helmet-shaped,” and the petals similarly affected. Maxwell Masters, op. cit., page 260.), by you be looked at as reversion to the columbine state? Would it be too bold to suppose that some ancient Linaria, or allied form, and some ancient Viola, had all petals spur-shaped, and that all cases of ”irregular peloria” in these genera are reversions to such imaginary ancient form? (660/3. ”'Regular or Congenital Peloria' would include those flowers which, contrary to their usual habit, retain throughout the whole of their growth their primordial regularity of form and equality of proportion. 'Irregular or Acquired Peloria,' on the other hand, would include those flowers in which the irregularity of growth that ordinarily characterises some portions of the corolla is manifested in all of them.” Maxwell Masters, loc. cit.)
It seems to me, in my ignorance, that it would be advantageous to consider the two forms of Peloria WHEN OCCURRING IN THE VERY SAME SPECIES as probably due to the same general law--viz., one as reversion to very early state, and the other as reversion to a later state when all the petals were irregularly formed. This seems at least to me a priori a more probable view than to look at one form of Peloria as due to reversion and the other as something distinct. (660/4. See Maxwell Masters, ”Vegetable Teratology,” 1869, page 235; ”Variation of Animals and Plants,” Edition II., Volume II., page 33.)
What do you think of this notion?
LETTER 661. TO P.H. GOSSE.
(661/1. The following was written in reply to Mr. Gosse's letter of May 30th asking for a solution of his difficulties in fertilising Stanhopea.
It is reprinted by the kind permission of Mr. Edmund Gosse from his delightful book, the ”Life of Philip Henry Gosse,” London, 1890, page 299.)
Down, June 2nd, 1863.
It would give me real pleasure to resolve your doubts, but I cannot.
I can give only suspicions and my grounds for them. I should think the non-viscidity of the stigmatic hollow was due to the plant not living under its natural conditions. Please see what I have said on Acropera.
An excellent observer, Mr. J. Scott, of the Botanical Gardens, Edinburgh, finds all that I say accurate, but, nothing daunted, he with the knife enlarged the orifice and forced in pollen-ma.s.ses; or he simply stuck them into the contracted orifice without coming into contact with the stigmatic surface, which is hardly at all viscid, when, lo and behold, pollen-tubes were emitted and fine seed capsules obtained. This was effected with Acropera Loddigesii; but I have no doubt that I have blundered badly about A. luteola. I mention all this because, as Mr.
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