320 



ORGANOGRAPHY. 



but one ovule, this may arise at the bottom of the ovary or 

 cell and be directed towards the summit, as in Compositse 

 and Polygonacese {fig. 713), when it is said to be erect; or 

 it may be inserted at the summit of the ovary and be turned 

 downwards, as in Hij^puris {fig. 714), in which case it is 



Fig. 713. 



Fig, 714. Fig. 715. Fig. 716. 



Fig. 713. Vertical section of the ovary of a species of Bumex (Polygo- 

 nacece). p. Enlarged calyx surroutiding the ovary. The ovary contains 

 a single, erect, orthotropous ovule. The embryo is inverted or anti- 



tropous. Fig. 714. Vertical section of the ovary of the Mare's Tail 



{Hlppuris vulgaris), o. Ovule, which is inverse or pendulous, and 

 anatropous. s. Baseofthe.etyle. /.Funiculus, r. Raphe, c. Chalaza. 



From Jussieu. Fig. 715. Vertical section of the ovary of the Pelli- 



tory {Parietaria officinalis), with a single ascending ovule. The 

 letters have the same references as in the last figure. From Jussieu. 



Fig. 716. Vertical section of the ovary of the Mezereon (Daphne 



Mezereum), containing a solitary suspended ovule. The letters refer 

 as before. 



inverse or pendulous ; or if it is attached a little above the 

 base, and is directed obliquely upwards, as in Parietaria {fig, 

 715), it is ascending; or if, on the contrary, it arises a little be- 

 low the summit, and is directed obliquely downwards, as in the 

 Mezereon {fig. 716), and Apricot, it is said to be suspended ; or 

 if from the side of the ovary, without turning upwards or down- 

 wards, as in Crassula, it is horizontal ov peltate. In some plants, 

 as in Armeria {fig. 623), the ovule is suspended from the end of 

 a long funiculus arising from the base of the ovary; such an 

 ovule is frequently termed 7'eclinate, 



In the above cases the position of the ovule is in general 

 constant, and hence this character is frequently of much im- 

 portance in discriminating genera and natural orders. Thus 

 in the CompositJie, the solitary ovule is always erect; while in 

 the allied orders, the Valerianacese and Dipsacacese, it is sus- 

 pended or pendulous ; — the two latter terms are frequently con- 

 founded by botanists. In the Polygonacea {fig. 713), the ovule is 

 also always solitary and erect ; and in the Thymelacese {fig. 716), 

 it is suspended. In other natural orders we find the position 

 varying in different genera, although generally constant in the 

 same ; thus in the Eosacese, the genera Geum, Alchemilla, &c. 



