Encyclopaedia of Gardening 185 



process would be inocuous if the stigma had been already fertilised^ 

 either by pollen from the same flower (self -fertilisation or selfing) , or 

 had been transferred by wind or bee from another flower; therefore 

 the anthers must be removed from the flower to be crossed before 

 the pollen is ripe and the blossom enclosed with a muslin bag. Those 

 who wish to hybridise systematically should study Mendel's laws. 



Hydrangea (hydran-gea, from hydor, water, and aggeion, a vessel, 

 in allusion to the cupped shape of the seed vessel. Ord. Saxifra- 

 geae) . The Hydrangeas are 

 hardy deciduous shrubs, and 

 some species are grown ex- 

 clusively in the open air; but 

 hortensis is much esteemed as 

 a pot plant, on account of the 

 large heads of pink blooms 

 which it produces. It is easily 

 raised from cuttings. Shoots 

 may be taken in spring, and 

 inserted singly in small pots 

 in sandy compost containing 

 leaf mould in a warm frame, 

 or shoots with buds may be 

 struck in autumn. When the 

 plants are well rooted they 

 may be shifted to 5 -in. or 6-in., 

 in which they may flower. 

 Loam, with a little decayed 

 manure or leaf mould, and 

 some sand, will suit, When 

 planted out in soil containing 

 iron the colour changes to blue. For pot plants use I oz. alum in i 

 gallon of water. Young pot plants may be wintered in unheated 

 frames. The species most commonly grown in pots is Hortensia 

 (hortensis), which is not quite hardy. There are several varieties 

 of it, notably Mariesii and Thomas Hogg. Paniculata granciflora 

 is a splendid hardy variety with white flowers in late summer. 

 Petiolaris has white flowers in spring, and is sometimes seen on an 

 outside wall in mild districts, but it is not quite hardy. See the 

 Botanical Magazine, t. 6788. 



Hymenocallis. See Pancratium under Bulbs. 



Hymenophyllum (hymenophyl-lum, from hymen, a membrane, 

 and phyllon, leaf. Ord. Filices). Filmy ferns. They thrive in peat 

 with Sphagnum moss, broken sandstone, and sand. They must 

 have a saturated atmosphere (see Ferns). Tunbridgense and 

 unilaterale are the best-known species. 



Hypericum, St. John's Wort (hyper-icum, from yperikon, on ac- 

 count of, and ereike, heath, from the habitat. Ord. Hypericineae) . 

 Useful hardy perennials, some herbaceous, others shrubby, with 

 dense green foliage and yellow flowers. The best species is caly- 

 cinum, the Rose of Sharon, for it will thrive on dry banks as well as 

 .under trees. It should be planted a foot apart in autumn if a close 



PROPAGATING HYDRANGEAS BY CUTTINGS, 



