64 GENERAL BOTANY 



this with any kind of organ, no plant has a leaf 

 in this position, and it does not arise as far as one 

 can see like a root or a branch of the shoot. We 

 may conclude that it is an organ sui generis i.e. 

 of its own kind specially developed on Melons and 

 similar plants for the purpose of keeping the seed-coat 

 open, though it might be an undeveloped root. This 

 is a very important principle which is of universal 

 application, and which we shall have continually to 

 use in the study of botany. When an organ differs 

 in character from the usual type, because put to a 

 different use, we say that it is homologous with the 

 type but a modified form. Thus the cotyledons of 

 the Castor and Melon are slightly modified leaves, 

 those of the Brown-bean are more modified, those of 

 the Pea and Broad-bean are still . more modified. So 

 also the curved connecting cotyledon of the Onion 

 and Date is a modified leaf or leaf-stalk ; and the 

 scutellum of the Maize, Cholam, Paddy, Wheat, Barley, 

 etc., is also homologous with a leaf but a very much 

 modified form. 



1 1 . Looking back on what we have studied we learn 

 what germination means that it is a very interesting 

 and complicated process whereby the embryo in 

 the seed emerges and develops into the young plant. 

 First water makes its way in through the micropyle 

 and causes the kernel inside to swell so that it splits 

 open the seed-coat. Then the embryo begins to grow, 

 the radicle, being nearest the micropyle grows out 

 first, and it is interesting to see that it shows its 

 root-nature from the very beginning by always turning 

 downwards deeper into the ground. 



