CHANGES IN THE OVULE 



57 



dehiscent fruit, the two valves separating 

 from the margins of the placentae at ma- 

 turity, leaving the latter attached to the 

 torus and to a false septum, which divides 

 the silique into two parts. The principal 

 modification of the silique proper is into 

 the lomentlike form which we have al- 

 ready considered. This class of loment- 

 producing plants are commonly found in 

 the vicinity of water, and their fruits are 

 adapted to transportation by this method. 

 A more important modification is into the 

 Silicle (Figs. 304 to 306), which differs 

 from the silique not only in being short 

 and broad, but in possessing ordinarily 

 some form of adaptation to wind or othrr 



transportation, thus belonging m our first 

 class. 



The Capsule U'igs. 240, also 271 to 

 283),— The typical capsule is to be defined 

 as a di to polycarpellary longitudinally de- 

 hiscent fruit. Prom the typical form, how- 

 ever, it varies in several directions to such 

 a degree as to render it impossible to 

 frame a perfect definition. The capsule 

 of the poppy (Fig. 307) opens by a num- 

 ber of small pores at the summit and this 



its character. The title must be supple- 

 mented by more or less of a description. 



CHANGES IN THE OVULE. 



As in the case of the parts entering into 

 the formation of the pericarp, so in that 

 of the part forming the seed— namely, the 

 ovule— It is well to precede our study of 

 the changes which it undergoes by con- 

 sideration of the objects to be attained 

 thereby. The essential feature of the aeed 

 is the possession as one of its parts of a 

 more or less rudimentary plant, developed 

 from the fertilized oosphere, and known 

 as the Embryo. During the period inter- 

 vening between the beginning and the 

 completion of seed-formation the embryo 

 requires nourishing, and provision for this 

 constitutes the first requirement of the 

 process. The further development and 

 growth of the embryo between the time 

 of germination and that of absorption by 

 it from the external world calls for addi- 

 tional nourishment. This can be met 

 only by the storage as a part of the seed 

 of an additional food supply. Protection 

 of the seed contents during its develop- 

 ment is only partially afforded by the 



forms. In other pericarp, and this office is supplemented 



cases the mode of opening is by various 

 forms of irregular dehiscence intermediate 

 between the longitudinal and lue eircum- 

 scissile. Finally, we must aote that 

 many fruits, like those of some species of 

 Passiflora, which possess no regular or 

 natural method of opening are still classed 

 as capsules by systematic botanists. 



The Pyxis (Fig. 30S).~A circumscis- 

 silly dehiscent fruit. 



The Syconium.— A fruit consisting of a 

 hollow branch, becoming fleshy, its inner 

 surface the receptacle for many small, 

 one-seeded akene-like fruits. 



The Aeterio (Figs. 262 and 263).— An 

 aggregate fruit, with an accrescent fleshy 

 torus and many crowded pistils. 



The Strobile (Figs. 310 and 311).— A 

 multiple dry fruit, its elements in the form 

 of imbricated scales. 



The Galbalus (Fig. 312).— A fruit simi- 

 lar to the last, but the scales fleshy or 

 much thickened above, so that the form 

 becomes more or less globular. 



In conclusion it may be remarked that 

 to assign a name to a fruit is insufficient 

 in most cases, especially those of ag- 

 gregate and multiple fruits, to designate 



by the coverings of the seed itself, while 

 its self-protection between the periods of 

 maturity and germination is a manifest 

 necessity- The transfer of the mature 

 seed to the point of germination, or its 

 Dissemination, and its fixation in a favor- 

 able site have already been referred to. 

 We have seen that in many cases these 

 offices are not provided for by the peri- 

 carp, and we must look for such provision 

 to the seed itself. The parts of the seed 

 by which these several offices are per- 

 formed we find to be as follows :^The 

 food supply during the germination of the 

 macrospore and development of the game- 

 tophyte we have seen to be the portion of 

 the nucellus external to the embryo-sac. 

 Usually more or less of this material re- 

 mains during at least the earlier period 

 of the development of the embryo and 

 contributes to the nourishment of the lat- 

 ter. Occasionally it persists even in the 

 seed condition- It is known as the Peri- 

 sperm. Inside the embryo-sac a further 

 store of nutriment is caused to develop 

 as a result of fertilization, this consti- 

 tuting the chief supply of the growing 

 embryo. More or less of this also may 



