342 ORGANOGRAPHY. 



ing to their respective origins. Otlier botanists again, instead 

 of using the two terms strophioles and caruncles as synonymous 

 with each other, apply the former term only when they proceed 

 from the hilum, and the latter to those from the micropyle. 

 Altogether, there is a great difference of opinion among bota- 

 nists, as to the application of the terms caruncles and strophioles ; 

 in this countiy they are more commonly understood in the sense 

 in which we have first defined them. 



2. The Nucleus or Ivernel {figs. 725 and 734, n). — The 

 nucleus of the seed corresponds to the same portion of the 

 ovule in a mature condition. In order to understand its 

 structure, we must briefly narrate the changes which the 

 nucleus of the ovule undergoes after the process of fertilization 

 has been effected. We have already stated, that at an early 

 period, a quantity of protoplasmic matter of a semi-fluid nature 

 is deposited in the embryo-sac. In this matter nuclei soon 

 make their appearance ; and their formation is succeeded by 

 the development of a number of loose cells ; these are first pro- 

 duced upon the walls of the embryo-sac, and their formation 

 extends gradually inwards. A similar development of cells 

 also frequently takes place on the outside of the embryo- sac, and 

 therefore in the nucleus itself, which is in such cases necessarily 

 thickened. These cells, Avhich contain nutritive matters of va- 

 rious kinds, are especially designed for the nourishment of the 

 embryo, which is developed in the sac after the process of fer- 

 tihzation. (See Fertilization.) 



The embryo, by absorbing the nourishment by which it is 

 surrounded, begins to enlarge, and in so doing presses upon the 

 parenchymatous cells by which it is enclosed, and thus causes 

 their absorption to a greater or less extent according to the 

 size to which it ultimately attains. In some cases, the embryo 

 continues to develop until it ultimately causes the destruction, 

 not only of the parenchymatous tissue of the embryo-sac, but 

 also of that of the nucleus, in which case it fills the whole in- 

 terior of the seed, and is coated directly by its proper integu- 

 ments, which have been just described. At other times, 

 however, the embryo does not develop to any such degree; in 

 which case it is separated from the integuments by a mass of 

 parenchymatous tissue of varying thickness, which may be de- 

 rived from that of the nucleus itself, or from the nucleus com- 

 bined with that of the embryo-sac according to the extent to 

 which the embryo has grown ; a tissue will thus remain, forming 

 a solid mass round the embryo to which tlic name of albumen 

 has been ajiplied; but as the nature of this substance is dittercnt 

 to that called by chemists vegetable albumen, it is l)etter to 

 designate it as the perisperm. As this albumen or pcrisperm is 

 sometimes formed both from the tissue of the nucleus, and that 

 of tiie embryo-sac also, it has been proposed to call the latter 



