60 



DOMESTIC BOTANY. 



a root called the radicle is also produced downwards, tlie 

 two lobes being cotyledons. 



In palms, cycads, grasses, lilies, &c., a wbite point or 

 teat is first seen to protrude, which, in ordinary seeds, is 

 short, but in palms lengthens from one to several inches, 

 or as in the double cocoa-nut, even to two feet in length ; 

 be this short or long, it is called the cotyledon, and con- 

 tains the plumule. In time its apex opens by a pore, 

 slit, or cleft, from which issues a green leaf, as also a 

 little rootlet {radicle), forming the basis of the future 

 plant, other leaves being successively produced. The 

 former of these modes of germination is called dicotyle- 

 donous (fig. 13, a), that is, having two seed lobes; the 

 latter monocotyledonous (fig. II, a), with one seed lobe. 



The cotyledons vary greatly in size, form, and texture^ 

 in different plants ; in the radish and cucumber they are 

 thin and green, being more leaf-like than in the bean. 

 The common mustard and cress afford a good example, 

 the part eaten as salad being the cotyledons, between 

 which the plumule is seen to arise to form the plant. 

 In the pea, bean, and horse-chestnut, they are thick and 

 fleshy. In general the cotyledons soon give up their 

 functions, and wither; but in the genus Streptocarpus, a 

 South African plant, with flowers like a Gloxinia, and the 

 remarkable Welivitschia mii'abUis, they increase in size, 

 in the former becoming quite a natural-looking leaf, six 

 or more inches in length, in the latter, more remarkable, 

 attaining the length of four or more feet ; in both cases 

 they perform the functions of leaves. 



In some dicotyledonous plants the seed lobes are so 

 closely united (connate) or consolidated, as in the Indian 

 cress, that they appear as one. In thick-skinned seeds, 

 such as acorn, sweet chestnut, and many of the Pea 



