1650 



A TEXTBOOK OF THEORETICAL BOTANY 



monogvna (Hawthorn), Mespilus germanica (Medlar), and Cydonia vulgaris 

 (Quince). 



Certain other common members are well known among British wild 

 flowers. Rosa canina (another general name embracing all the Dog Roses), 

 and R. riihiginosa (Sweet Briar), Fragaria vesca (Wild Strawberry), Potentilla 

 anserina (Silverweed), P. erecta (Tormentil), and P. sterilis (Barren Straw- 

 berry). Then there are the species of Geiiin: G. rivale (Water Avens) 

 and G. urbamim (Wood Avens), Agrimonia eupatorium (Common Agri- 

 mony), Filipendiila iilmaria (Meadowsweet) and many others. 



When we turn to garden plants the number of common or well-known 

 genera is far too great even to catalogue. Genera such as Cotoneaster and 

 Spiraea comprise dozens of species and far larger numbers of varieties. 

 Many have been grown for ornament and at least two bigeneric graft hybrids 

 between species of Crataegus and Mespilus have been successfully cultivated 

 (see Volume IV). 



With such a varied assemblage of forms it is obvious that the limits of 

 the family may be a matter of dispute, and while some retain them all 

 together in a single large family, others would prefer to separate them on 

 relatively minor points. 



The plants may be either herbs, shrubs or trees, woody types pre- 

 dominating. The leaves are alternate, simple or compound and usually 

 stipulate. Various types of vegetative propagation by means of runners 

 or suckers are common. 



The inflorescence may be either racemose or cymose or occasionally 

 the flowers may be solitary. 



Fig. 151 1. — Floral diagram of Pyriis 

 mains. Rosaceae. 



The flowers (Fig. 151 1) are usually hermaphrodite, regular and usually 

 pentamerous or more rarely tetramerous. They are generally perigynous 

 and sometimes epigynous (Fig. 15 12). 



The calyx is sometimes gamosepalous, composed of five or occasionally 

 four sepals. Sometimes there is an epicalyx, produced by the fusion of 

 sepal stipules in pairs below the true sepals, as in Fragaria. 



