406 



MB. F. DABWIN OX THE GLANDULAB BODIES OS 



the Acacia. But as far as my work goes, I know of no essential 

 feature by which a food-storing cell of Cecropia can be distinguished 

 from the similar cells of the Acacia. 



Development. —By cutting sections perpendicular to the free 

 surface of the young pulvinus, food-bodies in various stages of 

 growth are included in the preparations. The youngest condition 

 in which I have found these structures is that of slight excrescen- 

 ces above the surface, included within the epidermis, and formed of 

 cells differing in shape and in their granular aspect from the ordi- 

 nary chlorophyll-bearing parenchyma-cells of the pulvinus. This 

 condition of things is shown in fig. 5. These excrescences increase 

 in size, projecting as dome-like masses, and gradually assume the 

 characters of food-bodies. 



It is this method of development which induces me to believe 

 that the food-bodies of Cecropia, like those of Acacia, are of glan- 

 dular origin ; for it corresponds with the mode of growth of other 



glands 



door p. 114). I am aware that what I have said must seem but 

 slender evidence of the glandular nature of the food-bodies of 

 cecropia ■ it w, however, the only view of their homologies which 

 1 have been able to form . 



| 



If the view here advocated be the correct one, it completes in 



curious 



. i , x — "wwawcti, auu vecropta: more- 



over it renders the whole case more intelligible from the evolu- 

 tion stand-point. It is probable that the food-bodies of Acacia 

 were origmally glands whose function, like that of the serration- 

 glands of Kemke, was to lubricate the young leaves. But even 

 granting this, it is not easy to make out the steps by which they 

 could be converted into stores of nutriment. I believe that a 

 possable explanation may be found in an observation of Keinke's. 

 lie noticed that the glands on the footstalks of Prunm avium 



iWhlPh tT*r»rr» fV.^™ ~„ 'x* „ 



(which 



secreted nectar, and that the glands on the two or three lower 

 teeth of the leaf occasionally produced nectar instead of their 

 normal secretion (resin). Why, therefore, should not the glands 

 in which the food-bodies presumably took their origin have suf- 

 fered a similar change, so that oil was formed in the cells instead 

 of sugar or resin ? The storing of a product instead of its 

 elimination from a cell is not an essential point of difference 

 between the two cases. Moreover the ants may have com- 



