ON PROPAGATION BY SEED. 



241 



often happens, that when the cotyledons are fleshy, and ai"e destroyed by 

 insects or otherwise, the young plants are u-retrievably lost. As soon as the 

 testa or husk becomes soft and tender, the seed absorbs the surroundmg mois- 

 ture, and generally germinates very quickly, if it be not too old. If the husk 

 be, on the contrary, hard, or, as in many cases, stony, the moisture penetrates 

 only through the micropylus, and is communicated to the feculent part by the 

 root. In these cases the seeds lie sometimes very long in the ground with- 

 out germinating ; the absorption of moisture going on, in general, too slowly 

 to effect a quick and strong development, which is absolutely necessary to 

 burst those firm husks or shells which are bound together, as it were, by 

 sutures. These seeds are often lost when they lie for many years ; and, to 

 make sure of their germination, artificial means should be appKed. To 

 cause a rapid germination of the seeds of the acacia, soaking them in boiling 

 water has been applied of late years with success ; but, in general, this is a 

 very unsafe means, and may do more injury than good. The safest and 

 best way is to cut or file the hard shell, which it is only necessary to pene- 

 trate at one spot to the albumen or cotyledons. From this spot the seed imbibes 

 the requisite quantity of air and moisture, the radicle is quickly developed, 

 and, with the help of the swollen tissue within it, bursts the sutures of the 

 husk. In this, way many hard-shelled seeds of monocotyledonous and 

 dicotyledonous plants, such as canna, pseonia, acacia, abrus, erythrina, 

 cassia, schotia, guilandina, adenanthera, bauhinia, and caesalpmia, have 

 been made to germinate in a short time, mostly in from ten to twenty days. 

 If the seeds be old, they should, after cutting, be laid for a few days in 

 lukewarm rain-water, and, if they have any life remaining, this will sti- 

 mulate it. Something similar also takes place with seeds which, besides the 

 testa, or husk, are also enclosed in a pericarpium, or outer-covering. They 

 lie either in fours, at the bottom of a dry hollow cup, as in the labiatse and 

 boragfneae ; or they are single, or several, surrounded with a thick fleshy 

 cup, as in many species of the rosacese ; or single, or in twos, covered with a 

 dry cup, as in compositse, umbelliferae, and their allied species. Lastly, in 

 the graminese, we find them only surrounded with the pericarpium, as true 

 caryopses. Many of these germinate as easily as naked seeds ; but this depends, 

 in some measure, on the capacity or incapacity of the husk to absorb water 

 in a natural state. We find seeds hard and stony only among the rosacese, 

 as in rosa, prunus, cotoneaster, mespilus, cratse'gus, &c., and these require 

 cutting or filing, if intended to germinate quickly. The remainder are 

 divided, according to their formation, into two groups; those possessing 

 albumen, in which the embryo lies, and those that do not. This division is 

 useful, for the cotyledons always imbibe the water fii'st and easiest, whereas 

 the albumen is less hygroscopic ; and hence the germination of those seeds 

 which have none, but whose interior is entkely filled with the embryo and 

 its cotyledons, as in the boragiueae, labiatse, compositse, &c., will be more 

 easily effected. The graminese and umbelliferse, on the contrary, possess 

 albumen : in the former, the embryo lies outside of the albumen, on which 

 account they easily germinate ; whereas, in the latter, the embryo is entirely 

 surrounded by the albumen, for which reason, with the exception of most 

 of the annual or biennial sorts, they are more difficult to vegetate. As 

 these seeds cannot be cut with advantage, it is usual to sow them late in 

 autumn, with other difficult-growing sorts ; so that when the universal 

 period of germination comes, in the spring, they may be sufficiently pene- 



