122 CLASS-BOOK OF BOTANY. 
(b.) Monocotyledons have— 
(1.) One seed-leaf. 
(2.) Straight-veined leaves. 
(3.) Parts of the flower in 3s. 
Less prominent characters are as follows :— 
(a.) Dicotyledons have— 
(4.) Leaves usually petiolate, or, at least, with the 
blade rarely sheathing. 
(5.) Radicle of the embryo developing directly into a 
tap-root. 
(6.) In woody plants the wood appears in annual 
rings, owing to the mode in which certain 
formative tissues of the stems are developed. 
(Ex. Broad-leaf or Rata.) 
(6.) Monocotyledons have— 
(4.) Leaves usually with sheathing-bases. . 
(5.) Radicle of the embryo remaining undeveloped, 
and haying fibres growing out of its sheath, 
so that the first root is fibrous. 
(6.) In woody plants no annual rings are visible. 
(Ex, Cabbage-tree.) 
You will come across exceptions to these features: thus, 
some Dicotyledons have more than two seed-leaves (Persoonia), 
and sometimes some of the parts of the flower appear to be in 
3s (as in Dock, some Wattles, &c.); but these exceptions are 
not so numerous or so important as to overthrow the general 
rule. So also there are Monocotyledons with netted-veined 
leaves (Supple-jack), and some with fewer parts to their 
flowers than 3s, while others have their parts in 2s or 4s; 
but these exceptions are even fewer. So we may accept the 
above as our primary division, and arrange all our flowering 
plants mto one or other of these classes.” 
Let us now carry this subdivision further, and notice that 
our Dicotyledons fall into three groups or divisions, according 
to the structure of their perianth. Thus, one section, including 
all the plants referred to in chaps. I., IT., ITI., have their petals 
separate, and may be placed in one sub-class, called Poly- 
petalz; those referred to in chap. IV. have their petals united, 
and may therefore be placed in a second sub-class, Gamo- 
petalz ; while those referred to in chap. V. either have their 
corollas or their whole perianth wanting, and hence are placed 
in a third sub-class, called Incomplete. We can further 
* T purposely omit here Pines, Firs, and other coniferous plants, as 
I did in the preceding part of this book, as an examination of their 
structure could only be undertaken satisfactorily with appliances not 
usually to be found in schools, 
