1690 



A TEXTBOOK OF THEORETICAL BOTANY 



the Lilac, a member of the Oleaceae. Carpentaria californica, with large, 

 white flowers, is like Philadelphus but has a superior ovary (Fig. 1550). 

 Also belonging to this sub-family is the genus Hydrangea, several species 

 of which are grown in gardens. The flowers are produced in cymose 



Fig. 1550. — Carpentaria californica. Flowers. 



corymbs in which, in most cultivated forms, the flowers, or at least the 

 outer ones, are neuter and possess large petaloid calyces, giving the inflor- 

 escences a very conspicuous appearance. 



In the Escallonioideae the best-known genus is Escallonia, with about 

 sixty species, several of which are cultivated. They show a marked tolerance 

 to sea spray and are frequently planted in coastal districts to form ever- 

 green hedges. The genus is a South American one, found chiefly in the 

 Andes and the drier parts of southern Brazil. Phyllonoma, with one species, 

 occurs from Mexico to Columbia. PoJyosma, with thirty species, occurs in 

 Australia and south-eastern Asia, while Itea, with six species, occurs in 

 eastern Asia and also in North America. Several species are cultivated, 

 particularly /. ilicifolia (Fig. 1551) with evergreen spiny leaves. 



The genus Ribes contains about 140 species, many of which are common 

 in North America (Fig. 1552). The fact that members of this genus form 

 one of the hosts of the White Pine Blister Rust has led to wholesale des- 

 truction of the genus in the United States and Canada. We have already 

 referred to three species which are cultivated under the names of the 



