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RUDIMENTS OF THE NATURAL SYSTEM OF BOTANY. 
NO. VI. 
In taking another and final view of the elements which constitute the distin- 
guishing features of the Natural Orders, we are not without fear of having detained 
our readers too long on these preliminary matters, which, in the absence of any 
reference to plants that might illustrate them, must inevitably be more or less 
tedious. Although wanting, however, in intrinsic interest, it will be sufficient for 
the inquirer who has taken the trouble to peruse them, to know that the details 
into which we have entered, will render essential assistance when the Orders are 
individually laid open, and the objects of attraction they contain patiently elicited. 
Besides the characters of the stigmas before commented on, an additional and 
striking one exists, which is found in very few Orders. It is perceptible as a distinct 
membranous covering or case, entirely enveloping the organ, and bearing the name 
of indusium. The readers of Mr. Main's work on Vegetable Physiology will be 
in no danger of confounding what he has called the indusium with the appendage 
here described ; the membrane there intended being much more generally, in short, 
almost universally present, as the rudimentary layer between the annual depo- 
sition of wood and bark in Dicotyledonous plants, and which eventually forms the 
new alburnum and liber, or, still more remotely, the woody and cortical accretion. 
Some value is also attached to the position of the stigma, as to whether it be 
capitate (i. e. growing on the summit,) or on the side of the style. 
In the incipient stages of the seed's growth, and before it becomes invested 
with a conspicuous integument, it is so far considered distinct as to have the term 
ovule assigned it. It is important to regard the ovule apart from the seed in the 
study of the Natural System, because the former often possesses very prominent 
characters, which disappear, or are liable to deceive the examiner, when the organ 
is in a more advanced state. Several Orders are essentially characterized by having 
an indefinite number of ovules ; and others are quite as peculiar for having the 
number of them definitive. The situation of the ovules is, however, according to 
Dr. Lindley, " one of the most valuable forms of structure that can be taken into 
account." They are either attached to the interior base of the ovary or pericarp, 
and in that case are said to be erect ; or they hang from the top of the same 
member, and are then described as suspended. Two varieties of these dispositions 
occur, in which, on the one hand, the ovules are connected with the bottom of the 
ovary by a small process or stalk, when they are distinguished as ascending ; and 
on the other hand, if a similar protuberance is the seat of those depending from 
the summit, they are termed pendulous. Little use is made of these trifling 
deviations. 
As in almost every other instance, there are some striking departures from the 
rule which represents the ovules of certain Orders as growing in one direction, 
VOL. VII. NO. LXXXIII. L L 
