CHAP. II. 



KUDIMENTAKY COTYLEDONS. 



95 



Fig. 61. 



With the orange (Citrus aurantium) 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 

 hypocotyl was enlarged or swollen. 

 With Abronia umbettata 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, T Vth 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 umbellate : 



larger cotyledon ; but as the petiole ling twice natural size: 



, , f , . ' , . \ Al c, cotyledon ; c', rudi- 



of the latter increased in length mentaiy cotyledon ; h, 



and grew in the same line with 



the hypocotyl (7i), the rudiment 



appeared in older seedlings as if 



seated some way down the hypocotyl. With Abronia 



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, ns de- 

 scribed by Mr. K. I. Lynch 

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

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

 hypogean cotyledons is of im- 

 mense size ; the other is small 

 and soon falls off; the pair do not 

 always stand opposite. In another 



and very different water-plant, 

 Trapa wit cms, 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, 

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

 1832. 



