24. BOTANY. 
closely allied), as when itis too high (in those too little related). 
The complete accord between ‘‘illegitimate” descendants of di- 5 
morphous and trimorphous plants on the one side, and. hy brids of > 
different species on the other side, authorizes in fact such a group-'. a 
ing together under a common point of view of kinds of infertility 
occasioned by opposite causes. It is self-evident that the fact cen 
be merely expressed, but not explained. Likewise, naturally, only 
one of the many relations conditioning the greater or less fertility 
of a union can be expressed. i 
In a species the greater the difference of sexual elemi requi- ae 
site to the attainment of the highest degree of fertility, the greater 
will be, in general (ceteris paribus), the difference between the — a 
plants which can produce offspring with each other. In other, > 
words, species which, with pollen of the same stock, are wholly ~ 2 
sterile, and even with pollen of nearly allied stocks are more or 
less infertile, will generally be fertilized very readily by the pollen a 
of another species. The self-sterile species of the genus Abutilon, i 
which are, on the other hand, so much inclined to hybridization, - 
afford a good example ọf this theory, which appears to be con- z 
firmed, also by Lobelia, Passiflora and Oncidium oe 
I will not further present these general sbnerentiealt: “They : 
merely indicate in what sense, and in what connection I have wished : 
` to look upon the following example of infertility between en ae 
lations. , 
In the following A. C. E. F. M. P. denote six indigenous spe- 
Ges of Abutilon. >.: ', For indicating the simple hybrids the i 
letters of the united species are placed in juxtapositon withouy 
other signs, and the maternal species first. Thus EF 
a hybrid whose mother is Æ and whose father is F. In the - 
of union of these simple hybrids among themselves or with eH 
species, a point is placed between the aymbel of the mother, ae 
that of the father following; F. CF had, consequently, F for the 
mother, CF for the father; CH. S had CE for the mother 2 and 8 a 
for the father. Numbers placed under and at the right of the 
~ ters denote the individual ‘stocks of a species or a hybri 
A FS, FS, are, for example, three different stocks of the hybr m 
The four’ plants EF. F,, EF. F,, F. EF,, F. EF, are ben 
and sisters, having had the same parents F, and BPs S 
-Nine flowers of F. EF, dusted with pollen of other fow wers 
i eet fee wangle tt i 
tes sae 
es 
So ee aes 
