76 ON SEEDLINGS 



ovules which develop ; they are contained in a wooden capsule, 

 and are variously compressed. In Citrus also the cotyledons 

 are unequal and irregular, several embryos being contained 

 in each seed, and sometimes squeezed together in the utmost 

 confusion. 



In several other cases among those which have been 

 already referred to, we can hardly doubt, I think, that the 

 form of the cotyledon has been affected by the seed and not 

 vice versa. 



Let me in conclusion take one other illustration. The 

 cotyledons of the Sycamore (fig. 9) are long, narrow, and 

 strap-like ; those of the Beech (fig. 13) are short, very broad, 

 and fan-like. Both species are exalbuminous, the embryo 

 occupying the whole interior of the seed. 



Now in the Sycamore the seed is more or less an oblate 

 spheroid, and the long ribbon-like cotyledons, being rolled up 

 into a ball, fit it closely, the inner cotyledon being often 

 somewhat shorter than the other. On the other hand, the 

 nuts of the Beech are more or less triangular : an arrange- 

 ment like that of the Sycamore would therefore be utterly 

 unsuitable, as it would necessarily leave great gaps. The 

 cotyledons, however, are folded up like a fan, but with more 

 complication, and in such a manner that they fit beautifully 

 into the triangular nut. 



Can we, however, carry the argument one stage further ? 

 Why should the seed of the Sycamore be globular, and that 

 of the Beech triangular ? Is it clear that the cotyledons are 

 constituted so as to suit the seed ? May it not be that it is 

 the seed which is adapted to the cotyledons ? In answer to 

 this we must examine the fruit, and we shall find that in both 

 cases the cavity of the fruit is approximately spherical. That 

 of the Sycamore, however, is comparatively small, say f inch 

 in diameter, and contains one seed, which exactly conforms 

 to the cavity in which it lies. In the Beech, on the contrary, 

 the involucre is at least twice the diameter, and contains 

 from two to four fruits, which consequently, in order to 

 occupy the space, are compelled (to give a familiar illustration, 

 like the segments of an orange) to take a more or less tri- 

 angular form. 



