8 EXPLANATION OF THE TERMS USED 



Simple. Not compound. A leaf is simple when it is not divided into leaflets. 



Solitary. When one flower only is found in the axil of a normal leaf or at the 

 end of a shoot. 



Species. Plants which, given the same conditions of grov^rth, show no structural 

 difference from one another usually belong to the same species. Also, if the 

 seed is sown, the vast majority of the offspring will be practically the same as the 

 parents. Occasionally, however, there may be a marked difference in one or 

 two individuals. If these hand on their peculiar features to their offspring, a 

 new species is formed ; if they do not, we call the new kind a variety. Generally 

 speaking, therefore, a species breeds true, while a variety does not. Sometimes, 

 however, it is not easy to say whether a plant should be considered a variety or 

 a separate species. Moreover, a too literal interpretation of the breeding rule 

 would lead to a vast number of new species which to the ordinary man would 

 be practically indistinguishable from one another. The whole question of 

 species, varieties, and forms (differences due to differing conditions of growth) 

 is largely a matter of opinion. When different species hitherto isolated by dis- 

 tance or environment are brought together, they may lose their specific characters 

 and behave as varieties, or even forms. On the other hand, we know that there 

 is some factor in the seed, seemingly independent of outside circumstances, 

 which causes like to breed like, though exactly what it is no one knows. In this 

 book the number of species has been kept as small as possible by classing the 

 minor differences as varieties and generally ignoring the scientific arguments for 

 ranking them as species. 



Spike. Used generally for a long and narrow raceme, but strictly speaking a 

 raceme in which the individual flowers are stalkless. (Fig. 66 a.) 



Stamens (A). The special (male) organs of the flower concerned with the pro- 

 duction of pollen. They usually consist of several to many thread-like bodies, 

 each bearing at its end a pair of small yellow lobes (the anther), which contain 

 the pollen. At the time of fertilization the anther lobes split open and discharge 

 the pollen, or, as in the heath and rhododendron family, the pollen is discharged 

 through apical pores. The stalk is known as the filament. (Fig. 82 c.) De- 

 noted in the floral formulae by the letter A (from the Greek word androecium, 

 male part). 



Stigma. The extreme outer end of the style. (Fig. 82 c.) When the flower is 

 ripe for fertilization, the stigma is often sticky or feathery for the purpose of 

 catching and retaining the pollen. (Fig. 82 c.) 



Stipule. An appendage at the base of the leaf-stalk, usually one on each side and 

 often leaf-like. The small scar left by its fall is an important point in identifi- 

 cation. (Figs. II A and 90 a.) 



Style. An extension upwards of the ovary for the purpose of exposing the stigma 

 for the reception of pollen. (Fig. 82 c.) 



Sub-opposite. Nearly but not quite opposite. (Fig. 69 a.) 



Tendril. A coiled thread by which a climbing plant grasps an object for support. 



Terminal. At the end, as opposed to lateral. 



Three-nerved (3-nerved). A 3-nerved leaf is one in which three of the chief veins, 



usually the midrib and two side veins, are much larger than all the others. 



(Figs. 65 c and 68 j.) It is usually palmately veined, but not always so. 



(Fig. 126 c and H.) 

 Toothed. Evenly (Fig. 83 a and b). Unevenly (Figs. 82 h and 83 k). Closely 



(Fig. 83 b). Distantly (Fig. 83 e and g). Finely (Fig. 83 j). Coarsely 



