A NEGLECTED PART OF FIELD BOTANY. 65 
leaves, orbicular-oblong, obovate or cuneate ; (1) margin serrate, 
(2) entire or waved; (1) blade curled, reticulate, (2) rugose ; (1) 
stipules, minute or none, (2) none; (1) anthers yeilow brown or 
purple, (2) purplish; (1) catkins ^- — \ in., (2) — 1 in.; (1) cap- 
sule rarely pubescent, subsessile, (2) hoary, sessile. 
The only characters which are here at all pronounced, and 
not such as would seem to pass readily into each other, are the 
size of the catkins — the smallest of (2) being double the largest 
of (1), and the serrate leaf of (1) and the entire leaf of (2). But 
one can soon find varieties thus or nearly thus distinguished, 
e.g., in S. Myrsinites, the serrature varies from glandular-serrate 
to faintly serrate ; and 5 . repens has leaves entire or serrulate. 
From the preceding examples we may now define a species, 
according to Sir J. D. Hooker’s descriptions, as being known 
or recognisable by a collection of constant varietal characters taken 
from any organ or part of a plant. The question, therefore, now 
arises, How many varietal characters must a plant have to con- 
stitute a species? It is here where systematists differ so much, 
as the numbers may vary from one to many. 
In the case of the Geranium, we find that the author was 
satisfied with five. In the Willows there are about eight or nine. 
In former days a single, or_ at least very few characters were 
thought enough to make a species, and some continental botanists 
would seem still inclined to adopt that view. 
Now, what one wants to discover is the answer to the ques- 
tion, What is the connection between varietal characters and 
the environment ? If the latter can be proved to be their cause 
directly or indirectly, then the environment may be said to be 
the origin of species. If, on the other hand, the environment 
only favours the survival of the variety, we must look elsewhere 
for the origin of it. 
Let us now take a few examples from the Students' Flora 
to illustrate the importance of observing all the features of the 
environment. Thus, opening the book at hazard, the eye falls 
upon Agrimonia Eupatoria, subsp. odorata, “ from the Clyde and 
Perth, southward, local.” The question at once arises, What 
are the “local” circumstances or environmental conditions 
which have either caused or favoured the existence of that sub- 
species ? 
Sedum Telepliium, var. Fabaria. This is described as “ more 
slender, upper leaves all cuneate at the base, carpels not fur- 
rowed, very local ; ” while “ leaves rounded at the base, carpels 
furrowed” are given as the characters of the type. 
Where is it to be found ? What are the surrounding condi- 
tions ? Is the soil more humid or more arid ? Is it limestone, 
or silicious or argillaceous ? Is the locality near the sea or 
inland ? Of what elevation and exposure ? 
As another example, let us turn to Ononis spinosa. The 
variety “ horrida ” is a “maritime spinous form.” Maritime 
plants are generally, or at least very frequently, succulent, so 
