PROCEEDINGS OP THE PERTHSHIRE SOCIETY OP NATURAL SCIENCE, 
57 
The following papers were read :— 
1. “ On the Causes which determine the Distribution and 
Limitation of the Lower Animals.” By the Kev. 
Thomas Brown, Collace. 
It is not necessary, said the author, to occupy time in 
proving the necessity which there is for the movements 
of the lower animals being restrained, and for their being- 
confined within certain definite limits. For it must be 
evident to every one, that if they had been allowed to roam 
about without any check being imposed upon them, the 
ends which God had in view, both as regards man and the 
animals themselves, would have been entirely defeated. 
And instead of the peace and harmony which at present 
exist among the various orders of creatures around us, the 
direst confusion would have prevailed, terminating at last in 
the total destruction of many orders and species. Mr Brown 
then proceeded to point out some of the ways by which 
God accomplishes His purposes as regards the distribution 
and limitation of the lower animals, while He at the same 
time secures for them that freedom of will which, under 
certain restrictions, He has been pleased to bestow upon 
them, and promotes their happiness, 
2. “ The Modes of Dispersion of the Seeds of Scottish Wild 
Plants.” By Professor J. W. H. Trail, M.A., 
M.D., F.L.S. 
The subject that I have selected to put before you at 
this meeting is one of considerable interest and import¬ 
ance from several points of view. This interest is 
rendered still greater to evolutionists, alike by the effort 
to explain the origin of the various adaptations for disper¬ 
sion of seeds met with among plants, and by their bearing 
on the value of characters to the systematist in his en¬ 
deavours to approach a natural system of classification. 
Observation and experiment have shown that the vegeta¬ 
tive organs of plants (stems, leaves, &c.), vary greatly in 
most species when the conditions around them are changed, 
e.p., in poor or stony soil as contrasted with rich fertile 
ground, in open or in shady places, and so forth; hence the 
amount of importance attached to diversities in these 
parts is very limited. On the other hand, the organs of 
reproduction (i.e., flowers, fruit, and seeds), are less directly 
exposed to the influence of surrounding conditions; and, 
save in number, and to some extent in size, they are 
hardly modified by the influences that so markedly act on 
the organs of vegetation. Accordingly, they are found to 
be far more constant in form and in structure, and hence 
are chiefly used by systematists. But the flower and 
fruits, though but little affected by the causes above men¬ 
tioned, are yet exposed to influences from which the other 
parts are exempt. These seem to have in course of time 
had a great effect in modifying the structure of both 
flowers and fruit in many plants to suit the conditions 
under which they live. These influences as regards 
flowers have been studied by careful and enthusiastic ob¬ 
servers in Great Britain, but more especially in Germany ; 
and numerous works, some of great merit, have been 
written on them and on their effects. 
In the flowers the great requisite is the conveyance of 
the pollen from the anthers to the stigma, so as to fer¬ 
tilise the ovules. In many plants this is effected by the 
wind, but in others insects are the bearers of pollen ; and 
it is in these that we meet with the most striking and 
beautiful forms of flowers. There is reason to believe that 
very great modifications ofiorm and structure have been 
brought about in these in course of time, suiting them for 
visits of insects, the structure of which specially enables 
them to convey the pollen aright, while colour and size 
have also been greatly affected in the same way. Hence 
characters liable to such influences must be used with 
much caution. 
In the fruits modifications are beneficial for a new ob¬ 
ject, viz,, the wide distribution of the seeds, and the 
agents are for the most part different; hence the modi¬ 
fications resulting from their action are of a different 
nature. Frequently the result may be attained in closely 
allied plants by modification of distinct parts, while the 
same means may be employed in two or more plants not 
at all closely related. Therefore, care is required to 
distinguish between such adaptation?! resemblances and 
those due to relationship, as they are of very different 
value to the systematist and to the genealogical botanist. 
Examples of close resemblances in fruits of widely distinct 
species and of differences in those of closely allied species 
will be noted in the sequel. 
It is unnecessary to dwell long on the great advantage 
that plants derive from wide distribution of seeds. When 
widely distributed there is, it is evident, a greater likeli¬ 
hood of some being brought into favourable conditions for 
healthy and vigorous growth. On the other hand, how¬ 
ever favourable the conditions may have been to the 
parent plant, were all the seeds to fall close around it 
and to germinate there, it is evident that there could not 
be room for the healthy growth of the progeny. It is well 
known that the same crops cannot be grown for several 
years continuously without impoverishing the soil by the 
removal of certain ingredients that must be artificially re¬ 
placed to keep that soil fertile. The same holds good with 
wild plants; hence advantage ensues from the young plants 
