30 SEED-SOWING. 



this treatment would be certain death to many delicate seeds, 

 which will not germinate unless sown on the surface of moist 

 compost, and covered over, so that they are surrounded by 

 water in the state of vapour, a method commonly practised 

 with such delicate seeds as Primula, Gloxinia, Gesnera, 

 Calceolaria, and Achimenes. Whenever healthy seeds rot 

 instead of germinating, in nine" cases out of ten excess of 

 moisture in the soil, or irregular application of heat and 

 moisture, has caused such a result ; and it may be taken as a 

 rule that, the smaller and more delicate the seeds sown, the 

 less moisture is essential in the soil in or on which they are 

 placed. In the. case of old or unhealthy seeds, the best plan is 

 to sow them in dry soil, placing them afterwards in a genial 

 heat and moderately humid atmosphere, where they should not 

 be watered until signs of germination appear. In this way the 

 seeds are gradually supplied with moisture by the powers of 

 absorption or attraction possessed by all soils in proportion to 

 their dryness when placed in the moisture-laden air ; and this 

 plan will be found to succeed where any other fails. It is 

 customary to steep many strong-growing seeds, in order to 

 facilitate their germination ; and seeds with very hard coats may 

 be immersed in water heated to 200 Fahrenheit, the object in 

 this case being to partly decompose or loosen the tissues of the 

 hard seed-coat, and thus stimulate the seed to make a quicker 

 growth. 



Autumnal-harvested seeds from cold and temperate latitudes, 

 even when placed in suitable conditions as regards heat and 

 moisture, do not germinate so readily as if they had previously 

 been more fully exposed to frost and moisture ; and on this 

 point Dr Regel remarks that these natural conditions of ex- 

 posure appear to have the effect of disintegrating the nutritive 

 matter or carbon of the cotyledons, and so hastening the ger- 

 mination of the young plants. In a state of nature, Alpine plants, 

 and many of the plants of Northern Europe and Asia, are sown 

 in the snow ; and this is especially true of Primulas, Azaleas, 

 Gentians, many kinds of Pinks, to say nothing of Willows, 

 Brambles, Roses, and other forms of northern vegetation. 



" Exposed to the influence of water, heat, and air, the parts 

 of a seed soften and distend \ the embryo swells and bursts its 

 envelopes, extending the neck and bases of the cotyledons, 

 and finally emitting its radicle (root), which pierces the earth, 

 deriving its support at first from the cotyledons or albumen, but 

 subsequently absorbing nutriment from the soil, and communi- 

 cating it upwards to the young plant. The manner in which 



