10 



MORPHOLOGY 



20. Caulicle or Radicle, and Cotyledons. The name of radicle 

 was early applied to the axis of the embryo below the cotyledons, 

 on the supposition that it was the actual beginning of the root. 

 But its structure and mode of growth show it is not root (24, 

 44, 78), but a body of the exact nature of stem, from the 

 naked end of which the root is developed. Wherefore Caulicle 

 (Lat. cauliculus, diminutive of caul-is, stem) is 

 the appropriate name ; and it would be gen- 

 erally adopted, were it not that the older term 

 is so incorporated into the language of sys- 

 tematic botany (in which fixity and uniformity 

 are of the utmost importance) that it is not 

 easily displaced. It may be continued in 

 descriptive botany on this account, but in 

 morphology it is apt to mislead ; and the name 

 of caulicle, suggestive of the true nature of 

 the organ, is preferable. 1 The more fanciful 

 name of Cotyledons was very early applied to 

 what are now recognized as answering to the 

 leaves of the embryo : it has the negative merit 

 of suggesting no misleading analogy. 2 



21. Development of the Dicotyledonous Em- 

 bryo, i. e. the two-leaved embryo. This, in 

 the Red Maple (Figs. 5-8), usually germinates 

 in summer, shortly after the fruits of the season 

 have matured and fallen to the ground. It 

 differs from that of Sugar Maple in the crump- 

 ling instead of coiling of the cotyledons in the 

 seed. Referring the whole physiology of ger- 

 mination to that part of the work which treats 

 of Vegetable Physiology, the development of 

 the embryo into the seedling may here be described, taking that of 

 a Maple for a convenient type or pattern, with which other forms 



1 Linnaeus called it RosteUum, a name which, being etymologically mean- 

 ingless in this connection, is not misleading. The French botanists named it 

 Tigelle, diminutive of tige, stem: but some (like Mirbel) applied the term to 

 the developing axis above the cotyledons; others, to the early axis both 

 above and below them. The name Radicula originated with Gaertner. 



2 The name Cotyledon, which was adopted by Linnaeus, is a Greek word 

 for a cup-shaped hollow or cavity, also for a plant with thickish and saucer- 

 shaped leaves. It was primarily applied to the thickened " lobes " of the 

 embryo, the foliaceous nature of which was not recognized. 



FIG. 6. One of the twin winged fruits of Red Maple (Acer rubrum), with body 

 divided, to show the seed. 6. Seed extracted and divided, to show the embryo within. 

 7. Embryo partlv unfolded. 8. Embryo in early stage of germination. 



