VEGETABLE METAMORPHOSIS. 307 



cells united together, and it is only during germination that it exhibits 

 these different parts. In Monocotyledons, the embryo consists of a 

 single phyton, with a radicular merithal or radicle, a cauline or tigellus, 

 and a foliar or cotyledon. In Dicotyledons, the embryo consists of two 

 or more phytons united, with their foliar merithals (cotyledons) distinct, 

 while their cauline and radicular merithals form each a single organ. 



641. In tracing the various parts of plants, it has been shown that 

 all may be referred to the leaf as a type. This morphological law was 

 propounded by Linnaeus and Wolff, but it is to Goethe we owe the full 

 enunciation of it. Vegetable morphology, the study of forms, or the 

 reference of the forms of the parts of plants to the leaf, is now the 

 basis of organography ; and it will be observed, that in considering the 

 various organs, this has been kept constantly in view. The calyx, 

 corolla, stamens, and pistil, are only modifications of the leaf adapted 

 for peculiar functions. It is not meant that they were originally leaves, 

 and were afterwards transformed; but that they are formed of the 

 same elements, and arranged upon the same plan, and that in the 

 changes which they undergo, and the relation which they bear to each 

 other, they follow the same laws as leaves do. The different parts 

 of the flower may be changed into each other, or into true leaves ; or, 

 in other words, the cellular papilla? from which they are formed are 

 capable of being developed in different ways, according to laws which 

 are still unknown. These changes may take place from without in- 

 wards, by an ascending or direct metamorphosis, as in the case of petals 

 becoming stamens ; or from within outwards, by descending or retro- 

 grade metamorphosis, as when stamens become petals. 



642. Bracts are very evidently allied to leaves, both in their colour 

 and form. Like leaves, too, they produce buds in their axil. The 

 monstrosity called Hen and Chicken Daisy, depends on the develop- 

 ment of buds in the axil of the leaves of the involucre. The sepals 

 frequently present the appearance of true leaves, as in the Eose. The 

 petals sometimes become green like leaves, as in a variety of Ranun- 

 culus Philonotis, mentioned by Decandolle, and in a variety of Cam- 

 panula rapunculoides, noticed by Dumas. At other times they are 

 changed into stamens. Decandolle mentions a variety of Capsella 

 Bursa-pastoris, in which there were ten stamens produced in conse- 

 quence of a transformation of petals. The stamens in double flowers 

 are changed into petals, and in Nymphsea alba there is a gradual 

 transition from the one to the other. Sometimes the stamens are 

 changed into carpels, and bear ovules. This has been seen in Wall- 

 flower, some Willows, Poppy, &c. Petit-Thouars noticed a plant of 

 Houseleek, in which the one half of the anthers bore ovules, and the 

 other half pollen. The carpels, as in the double Cherry, may be seen 

 in the form of folded leaves ; in double flowers they are transformed 

 into petals, and in other cases they are developed as stamens. It is 



