EXPLANATION OF THE TERMS USED 5 



families into Orders (not referred to in this book), orders into Sub-classes, 

 sub-classes into Classes, and classes into Subdivisions. (For convenience 

 Gymnosperms and Cryptogams are ranked as Classes in this book, though they 

 are really subdivisions.) 



Gland. A small swelling often found on leaves or other parts of plants, and usually 

 secreting oil or some other substance. 



Glaucous. Covered with bloom (like a plum) or grey or white substance as distinct 

 from hairs. 



Graft. The artificial union of two different kinds of tree or shrub by making an 

 incision in one and inserting a small branch of another. In the vast majority of 

 cases the two kinds thus united retain their distinctive characters. Where they 

 do not, the result is known as a graft hybrid. The best-known instance of this 

 is the Purple Laburnum, which is the result of grafting the Purple Broom on the 

 Common Laburnum. 



Head. A dense cluster of flowers or fruits. ^ (Figs. 14 e and 30 a and b.) 

 Hybrid. When the flowers of one kind of tree or shrub are fertilized by the pollen 

 from another kind — it may be a different variety, or species, or even genus — 

 the resulting offspring, if any, is termed a hybrid. Hybrids, while usually 

 combining the characters of both parents, often reveal entirely new characters, 

 such as more luxuriant growth, or showier and more abundant flowers; on the 

 other hand, they seldom breed true, if they breed at all, and have to be increased 

 by division. Most of the hybrids included in this book are important enough 

 in the garden and field to be treated as separate species, though botanically they 

 cannot be regarded as such. A natural hybrid is one produced without the 

 conscious agency of man; they are very common, for instance, among the 

 willows, poplars, elms, and veronicas, and make it much more difficult to sort 

 out the species belonging to these genera. 



K. See Floral Formula and Calyx. 



Lance-shaped (lane). Shaped like a lance head, i.e. with curved edges narrowing 

 at the base and apex and much longer than broad. If a leaf is at least three times 

 longer than broad, it can be taken as lance-shaped for the purposes of this book, 

 regardless of its actual outline (but see Linear and Ovate). (Figs. 40 and 58 D.) 



Lateral. At the side, as opposed to terminal. 



Leaflet (Iflt.). See Compound Leaf. 



Linear. Long and very narrow, with nearly parallel margins and narrowing at the 

 base, e.g. a blade of grass. (Figs. 50-53.) 



LoBED. Divided into segments the spaces between which do not reach the axis or 

 centre. There is no hard and fast distinction between lobes and large teeth. 

 (Figs. 23-36.) 



Midrib. The largest vein of a leaf, usually running lengthwdse along the axis from 

 base to apex. 



Monocotyledon. See page 282. As the term is used in the key to the illus- 

 trations, a few words here may not be out of place. The term covers a large 

 class of closely allied plants. Every gardener knows how the seeds of grasses, 

 onions, and leeks send up a single narrow leaf instead of the double and multiple 

 leaf of most other seeds. It is this character which gives the class its name 



^ A head formed of stalkless flowers borne on the swollen end of the axis is known as a 

 capitulum. (Figs. 67 D and 99 L.) 



