Chap. 11. 



RUDlMENTARy COTYLEDONS 



95 



Fig. 61. 



With the orange (Citrus aurantiuni) the cotyledons are 

 hypogean, and one is larger than the other, as may 

 be seen in A (Fig. 60). In B the inequality is rather 

 greater, and the stem has grown between the points 

 of insertion of the two petioles, so that they do not 

 stand opposite to one another ; in another case the 

 separation amounted to one-fifth of an inch. The 

 smaller cotyledon of one seedling 

 was extremely thin, and not half 

 the length of the larger one, so that 

 it was clearly becoming rudimen- 

 tary.* In all these seedlings the 

 nypocotyl was enlarged or swollen. 

 With Ahronia unibellata one of 

 the cotyledons is quite rudimen- 

 tary, as may be seen (c) in Fig. 61. 

 In this specimen it consisted of a 

 little green flap, f'Tth inch in 

 length, destitute of a petiole and 

 covered with glands like those on 

 the fully developed cotyledon (c). 



At first it stood opposite to the Abronia umbellita : seed- 

 larger cotyledon ; but as the petiole I'ngtw'ce natural size: 

 ° ;; . J • 1 .,1 "' cotyledon ; c , ludi- 



01 the latter increased m length mentaiy cotyledon ; h, 



and grew in the same line with 



the hypocotyl (h), the rudiment 



appeared in older seedlings as if 



seated some way down the hypocotyl. With Ahronia 



arenaria there is a similar rudiment, which in one 



enlarged hypocotyl, 

 with a heel or projec- 

 tion (//) at the lower 

 end; r, radicle. 



* In Pachira aquatica, as de- 

 Boribed by Mr. K. I. Tjynch 

 ('Journal Linn. Soc. Bot.' vol. 

 xvii. 1878, p. 147), one of the 

 hypogean cotyledons is of im- 

 mense size ; the other id small 

 and snon falls off; the pair do not 

 always stand opposite. In another 



and very different water-plant, 

 Trapa nalans, one of the cotyle- 

 dons, filled with farinaceous 

 matter, is much larger than the 

 other, which is scarcely visible, 

 as is stated by Aug. de Candolle, 

 ' Physiologie Ve'g.' torn. ii. p. 834, 

 1832 



