ORGANS OF REPRODUCTION. 559 



224. At subsequent periods the plant, which is gradually deve- 

 loped from the embryo, is decidedly nourished by the embryo- sac, and 

 even afterwards, in the later stages of germination, the assimilated 

 substances deposited in the endosperm serve for the sustenance of the 

 plant. The nucleus of the bud performs a similar function with the 

 perisperm, and acts as a substitute for the latter. The envelopes of the 

 bud are converted into the testa of the seed, and protect the delicate 

 germinating plant; the envelopes of the fruit perform the same 

 function, and subsequently assist in the distribution of the seed by 

 means of their hygroscopicity. The succulent parts of the fruit 

 may also serve, through their decay, to form a nutritive soil for the 

 first development of the young plant. 



Conclusion. 



The insufficiency and deficiency of our generalisations in Botany 

 are acknowledged by all competent investigators. It was believed 

 that more favourable results might be expected as Physiology and 

 Anatomy advanced, and systematic Botany looked for aid from the 

 same sources. The meagreness of our Physiology, freed from 

 all that does not properly belong to it, as I have endeavoured to 

 give it, affords but little hope at present from that quarter. It 

 cannot have escaped the notice of the attentive reader of the Mor- 

 phology, that little also can be expected from Anatomy. Whence, 

 therefore, are we to look for help ? By the study of external forms ; 

 not in the manner that it has hitherto been done, superficially 

 and without fundamental principles, but from the study of Mor- 

 phology as a science, whose leading principle must be the history of 

 development. It has been my object in the present work to indicate 

 the proper path, and to open an entrance into it according to the 

 best of my ability. May better men continue the work ! 



