12 
POPULAR SCIENCE REVIEW. 
where our weeds, such as Chick weed, Shepherd’s-purse, Lepidium 
ruder ale, Malva rotundifolia , Solarium nigrum , etc., etc., have 
established themselves ; and the inference I draw is, that assum- 
ing other plants to have travelled with them, those which were 
entirely dependent upon insects have perished, as they were not 
visited ; while those that were independent, as being capable of 
self-fertilisation, were the best fitted to survive in the struggle 
for life. 
The conclusion I have arrived at is that self-fertilisation is 
the aim of plant-life, so far as propagation is concerned ; that 
the existence of sexes enables a plant to diffuse itself by the 
production of independent offspring (seeds) far more readily and 
abundantly than by bulbs, and other vegetable offshoots; and that 
the chance of crossing is thus secured which induces variation 
in the offspring with greater rapidity than would spontaneously 
take place under self-fertilisation alone. 
The cross may bring with it some new physiological pecu- 
liarities, which impart a temporary stimulus to vegetative 
vigour ; but there is nothing to prove that this effect is of 
permanent value. I believe that by the local irritation induced 
by insects, all the vast diversity of beauty of form, and mar- 
vellous adaptations have been effected ; but that this last, though 
vastly enhancing nature from the human point of view, is of no 
real value, but is often a detriment to the plant itself. Hence 
I regard self-fertilisation as being proved to be the best condition 
in plant-life, to enable a species to maintain its existence in the 
great struggle for life in the world. 
DESCRIPTION OF PLATE I. 
Fig. ]. Pistil of Capsella JBursa-pastoris to show the capitate form of stigma 
characteristic of self-fertilising Crucifer ce. 
„ 2. The stigmas of Fumaria officinalis ; one of them is covered with 
pollen-grains. 
„ 3. One of the greups of anthers, which form a three-sided chamber in 
which the horn-like stigmas lie and are thus directly pollinated. 
„ 4. Bud of a cleistogamous Violet with the calyx removed, from a strong- 
growing garden plant. 
„ 5. A spurred petal from another hud. 
„ 6. A stamen retaining the nectariferous appendage, from the same. 
„ 7. Pistil from the same, with curved style. 
„ 8. Rudimentary petals of a cleistogamous bud of a wild form of Violet. 
„ 9. Stamen from same. 
„ 10. Pistil with the anthers coherent above, having been detached and 
elevated by the swelling of the ovary. 
„ 11. Pistil with anthers removed. 
