GENERATION. 139 



ment cannot be denied, as possessing claims to the atten- 

 tion of every one, both on account of the authority 

 which the names of their highly reputed authors con- 

 vey, and the most evident foundation in facts, according 

 to them, from which their opinions are derived, as shown 

 by the microscopical observance of the minute structure 

 of the plants which they have examined. 



241. According to Schleiden, a cellule in the interior 

 of the nucleus, at first differing in no way from the other 

 cellules, developes itself in a disproportionate manner 

 soon after the evolution of the primine and secundine, 

 or coats of the ovule, and presses upon the nucleus, the 

 parenchyma of which is absorbed from the interior 

 towards the exterior. This cellule is the sac of the 

 embryo (membrana amnii Malp. sac embryonnaire 

 Brong. quintine Mirb.) and exists in all the flowering 

 plants, without exception before fecundation. 



b. The contents of the sac of the embryo are a for- 

 mative matter for the cellular tissue, which, sooner or 

 later, often before fecundation, developes itself in the 

 sac, and when not absorbed, during the growth of the 

 embryo, forms the endosperm, (Albumen of most 

 authors.) 



c. The grain of pollen consists essentially of a sim- 

 ple cellule, the membrane of which is as thin and trans- 

 parent as water, and moreover in a state of vital de- 

 velopment. The contents are fecula mucilage, or gum, 

 in a word, the formative matters for cellular tissue ; all 

 the rest is indifferent and accidental to the character of 

 the grain of pollen. 



d. The ovary is always in free communication with 

 the exterior ; and when a true style exists, it is along its 

 canal this communication is seen. 



242. A cellular tissue, more or less peculiar, covers 

 the placenta, the internal walls of the ovary, and the 

 canal of the style, and terminates in the papillae of the 

 stigmata. This cellular tissue is the conducting tissue. 



e. At the period of fecundation, the conducting tissue 



