397 



evidently turning towards the base of the ovulum : a, nucleus ; 6, border 

 of secundine. 



Fig. 21. An ovulum of the same, after fertilisation. In the interval between 

 this state and the last, the primine has grown over the secundine and 

 nucleus ; the apex of the latter has turned completely to the base of the 

 ovulum ; and the foramen is contracted into the little perforation at a. 



Fir/. 22. Ovulum of Euphorbia Lathyris, in a very young state, long before the 

 expansion of the flower : a, kind of cap projecting from the wall of the 

 ovarium, and into which the apex of the nucleus (6) is inserted : this hood 

 finally closes over the foramen, into which it protrudes as the nucleus 

 retreats ; e, the primine ; the secundine is a similar cap included within 

 the primine. 



Fig. 23. Very young ovulum of Ruta graveolens : a, the primine ; b, the 

 secundine ; c, the nucleus. In the end, the primine extends, contracts at 

 its foramen, and closes over the secundine and nucleus. 



Fig. 24. Vertical section of an ovulum of Alnus glutinosa : a, the umbilical 

 cord ; 6, foramen ; c, primine (and secundine perhaps united with it) ; 

 <7, nucleus ; e, vessels of the raphe ; /, place of the chalaza. 



Fig. 25. An oblique vertical section of the fertilised ovulum of Tulipa Gesneriana : 

 a, foramen of the primine (or Exostome) ; &, foramen of the secundine (or 

 Endostome) ; c, primine ; d, secundine ; e, nucleus, its apex concealed 

 within that of the secundine ; /, vessels of the raphe ; g, place of the 

 chalaza. 



Fig. 26. Ovulum of Lepidium ruderale ; after A. Brongniart : a, umbilical 

 cord ; J, foramen ; c, point of the nucleus seen through the primine and 

 secundine. 



Fig. 27. Half-ripe seed of the same, cut through perpendicularly ; after 

 Brongniart : a, the umbilical cord ; 6, foramen ; c, primine ; d, secundine ; 

 e, nucleus ; /, embryo partially formed, its radicle pointing to the foramen ; 

 g, the point where the nourishing vessels of the placenta expand (the 

 chalaza). 



Fig. 28. A perpendicular section of the ripe seed of the same; after A. Brong- 

 niart. The primine and secundine are consolidated, and the nucleus is 

 entirely absorbed by the embryo, a, Umbilical cord ; &, foramen, now 

 become the micropyle ; g, chalaza ; k, cotyledons of the embryo ; i, radicle ; 

 fc, plumula. 



Fig. 29. Mode of fertilisation in Cucurbita Pepo ; after Adolphe Brongniart : 

 a, a portion of the placenta ; 6, ovulum ; c, its foramen ; d, the bundle of 

 stigmatic tissue through which the fertilising matter is conveyed, and to 

 which the foramen is closely applied ; e, the bundle of vessels that 

 communicates with the umbilicus ; /, the commencement of the raphe. 



PLATE VI. 



Fig. 1. A, Vertical section of the seed of Canna lutea : a, albumen ; 6, embryo. 

 B, Embryo extracted and divided vertically: a, cotyledon; 6, plumula 

 concealed within the embryo; c, radicle, with internal rudiments of 

 roots. 



