36 BOTANY. 



omphalode, or else pass under the external integument in the form of a raj)he 

 to the chalaza, when this is not coincident with the hilum. The terms, 

 orthotropal, campylotropal, anatropal, face, hack, «fee, already explained 

 under the head of the ovule, appl}' equally to the seed. 



As the embryo increases in size, it causes an absorption of cellular matter 

 from the embryo sac ,and nucleus, to such an extent as sometimes to reduce 

 these to the condition of a thin integument, in which case the seed consists 

 of embryo and integuments alone. A peculiar substance, termed albumen, 

 is frequently formed around the embryo, which, when developed within the 

 embryo-sac alone, is known as endospermic albumen, or endosperm ; and 

 when within the cells of the nucleus alone, perispermic albutnen, or peris- 

 perm. Sometimes both kinds occur in the same seed : when the embryo 

 occupies the Avhole seed, this is exalbnininoiis ; albuminous, when there is a 

 separate deposit of albumen. The object of the albumen is to supply food to 

 the embryo at the period of germination. It varies much in its nature, being 

 farinaceous, or mealy, consisting of starchy cells, as in the grains ; fleshy, or 

 cartilaginous, as in the cocoa-nut ; and horny, as in some palms, and in coflFee. 

 When the cellular tissue combines with the albuminous matter so completely 

 as to form but one substance, the albumen is solid ; ruminated, when a portion 

 of the tissue remains unconverted, causing a mottled appearance, as in the 

 nutmeg. The albumen consists, chemically, of oily matter, starch, and 

 nitrogenized compounds. 



The embryo consists of cotyledons, or rudimentary leaves ; the plumule, 

 or ge?nmule, which represents the ascending axis ; the radicle, or the germ 

 of the descending axis ; and the point of union of the two, or the collum. 

 The part intervening between the collar and cotyledons is the caulicule, or 

 tigelle. The embryo varies in its structure in different divisions of the 

 vegetable kingdom. Thus, in acrogens and thallogens it continues to be a 

 cell or spore, with granular matter in the interior, without any cotyledons ; 

 hence such plants are said to be acotyledonous. In endogens and exogens, 

 on the other hand, there is a distinct separation of parts in the embryo, the 

 former having, however, but one cotyledon {monocotijledonous), the latter 

 two {dicotyledonous). In the spore of the acotyledonous plant germination 

 takes place in any part of the surface. Sometimes spores are united in 

 definite numbers by a cellular covering, called j^^^ispore, or .^poridium, ; the 

 tetraspore of the Algse consists of four spores thus united. 



The first part formed in the embryo is the axis, having one of its 

 extremities turned towards the suspensor, and indicating the point whence 

 the radicle is to proceed; the other end pointing in the opposite direction, 

 and answering to the stem. From the point Vfhere the cotyledons are 

 united to the axis a bud is developed (as from tlve axils of leaves) ; this 

 contains the rudiments of the true or jirimordial leaves of the plant, and is 

 known as the gemmule, or plumule. This bud may usually be seen lying 

 within the cotyledons. In the monocotyledon the gemmule is usually 

 inclosed by the mostly cylindrical cotyledon at its lower portion. The form 

 of the dicotyledonous embryo varies considerably, but is always distin- 

 guishable from the monocotyledonous by a division at the cotyledonary 

 36 



