16 



MANUAL OF BOTANY 



form in most Fungi and Algse ; is that of the gametophytes of 

 the Ferns and most other vasctilar Cryptogams and of the 

 Flowering Plants. The sporophyte is less frequently a thalltis, 

 but this is the case in such of the Algae as possess one, and in 

 a few exceptional cases in the Phanerogams ; e.g. Woljffia arrhiza, 

 LojpJiogyne, etc. 



COEMOPHYTES. 



For many reasons it is most advantageous to commence the 

 study of the morphology of cormophytie plants with the most 

 highly differentiated forms. These are to be met with in the 

 great group of the Phanerogams, and in particular in the section 



known as the An- 

 l'i«- l**- Jig, 17. giosperms, to which 



all our ordinary 

 plants with con- 

 spicuous flowers be- 

 long. The promi- 

 nent form in these, 

 as we have seen, is 

 the sporophyte. 



If we examine the 

 seed of one of these 

 Angiosperms, e.g. 

 that of the common 

 Pea, we find it con- 

 tains the embryo or 

 young plant in a rudimentary orm. This embryo is shown in 

 fig. 16. It consists of a distinct central axis, t, which is some- 

 times called the tigellum, the lower part of which is known as 

 the radicle, r ; the upper part, which bears two or three rudi- 

 mentary leaves, is known as the plmnule, n. This axis is united 

 to, or bears, two fleshy masses, or lobes, which are its leaves 

 or cotyledons, c. The part between the attachment of the cotyle- 

 dons and the radicle is sometimes called the hypocotyledonary 

 portion or hijpocotyl, and the portion above the cotyledons, the 

 epicotyledonary part or epicotyl. Plants, like the Pea, which 

 bear two cotyledons, are gi'ouped together to form a great class 

 known as the Dicotyledons. Other embryos are found in some 

 seeds which possess only one cotyledon. Such are the embryos 

 of Grasses (fig. 17). These plants form another great group 

 known as the Monocotyledons. 



"When such a seed as the Pea is placed under favourable con- 



Fig. 16. DicotyleJouous embryo 

 of the Pea, laid open (magni- 

 fied), r. The radicle. I. The 

 axis (hypocotyl), terminated by 

 the plumule, it, c, c. The cotyl- 

 edons. Fig. 17. Section of 



the fruit of the Oat. p. Plu- 

 mule, r. Radicle, s. Scutellum. 



