SIR J. LUBBOCK — PIITTOBIOLOGICAL OBSERVATIONS. 



315 



I propose, however, to-day to suggest reasons whicli may account 

 for some, at any rate, of these differences. 



In the Memoirs to which I have already referred, I have dis- 

 cussed the causes whicli regulate the forms of seeds, and will not 

 now therefore enter into them- I may just, however, observe 

 that the shape of the cotyledons seems to have little, if any, 

 influence on the form of the seed. 



Fig. 3. 



Fig. 4, 



Seedling of Mustard (Brassica. 



nigrdf^ X 3. 



Seedling of Cyss (Z£p2' 

 diiim sativum), X 3. 



Forms of Ovules. 

 It may be convenient that I should shortly define a few tech- 

 iiical terms which I shall have to u?e frequently. Jhe fruit con- 

 sists of the ovary and whatever other parts perdst when the seed 

 is ripe. The seed is the or?/Z<^ fertilized by the pollen. The tesla 

 is the outer shell or coat of the seed. The mici^pyle is a small 

 opening through which the pollen-tube obtains access to the 

 interior of the ovule. The/wnic/e is the stalk by which the seed 

 is attached. The hilum is the scar left on the seed at tiie point 

 ^^here it was attached to the funicle. The chalaza is the spot to 

 which the nutritive vessels reach before ramifying in the seed. 

 lu some geeds the chalaxa and hilum coincide; when this is not 



