30 INTRODUCTION. 
at once referred to their proper groups. The position of the ovary in 
respect to the calyx has been already adverted to; this character is 
generally expressed by the terms inferior or superior ovary. The 
presence or absence of partitions in the ovaries is a very important dis- 
tinction. An ovary may be one-celled, because it consists of but a single 
carpel; or being syncarpous, it may contain an undivided cavity, from 
the obliteration of the partitions, or dissepiments, originally formed by 
the walls of the several adhering carpels. In this case the attachment 
of the ovules, or placenta, is either central, the ovules being clustered 
around a central column, or parietal, where they are attached to the 
outer wall. Varieties of structure of this nature are very important in 
- distingnishing orders. A peculiar enlargement of the receptacle which 
sometimes expands between the bases of the carpels so as to separate 
them more or less completely as in the Strawberry, is often very char- 
acteristic of particular orders. The ripened ovary or fruit exhibits 
numerous and remarkable differences in its form, substance, and mode 
of dehiscence (or its manner of bursting when ripe;) but these do not 
usually receive much attention from Botanists; since although there are 
a few orders which are charicterized by a particular kind of fruit, most 
others present numerous varieties among their different genera, 
35. Many valuable characters are drawn from the seed, both in its 
early and mature conditions. The number of ovules—that is to say, 
whether they are definite or indefinite—is frequently an important 
difference; still in some orders, there are genera nearly allied, in onc 
of which the number is definite, whilst it is indefinite in the other. 
The position of the ovules is more essential than their number ;—the chief 
distinctions are between those which, rising upright “from the base 
of the cavity, are termed erect ; and those, which hanging from its top, 
are called pendulous. Between these two conditions, however, there are 
other intermediate ones. Such a difference in the position of the ovules 
often serves to mark a distinct line of separation between the plants of 
two groups that are otherwise nearly allied. In the perfect seed, the 
number of cotyledons is a character of primary importance, for distin- 
guishing the two great classes of Phanerogamia, as already several times 
stated. Even this, however, is subject to occasional exceptions, for 
there are Endogenous plants with two cotyledons and some Exogens 
with only one or even none, whilst again, some Exogens have several, 
As a means of distinguishing orders the presence or absence of a 
separate albumen is a character of great value, especially when the 
embryo bears a very small proportion to it in amount. Where, how- 
ever the embryo and albumen are nearly equal in size, the character is 
of less importance; so that it is not uncommon to meet, in the same 
genera, of which the embryo alone fills the seed, and with others in 
