The Morphology of Ruppia Maritima. 



107 



with the stem and squeezed out of the coleorrhiza, producing the 

 ruptured end of the latter. In this figure the coleorrhiza had attained 

 approximately its maximum development. It then, with its enclosed 

 root, appears to the naked eye as a small, smooth, blunt projection 

 at the node. A photograph of a longitudinal section of this stage 

 is shown in Text-fig. 24. 



In the course of its growth the young root breaks through the 

 coleorrhiza, which then remains at its base as a collar-like structure 

 (PI. VIII, fig. 45; Text-fig. 21). 



An interesting incidental point in relation to the coleorrhiza, and 

 one which indeed may be connected with its function, is the 

 occurrence in its surface layer (when of 

 more than one layer in thickness) of cells 

 which are evidentl}- secretion cells (Text- 

 fig. 25). 



It will be seen from the above de- 

 scription of the coleorrhiza in Ruppia that 

 it is of entirely different nature from that 

 to which Sachs (1875, 1. c.) alludes. It has 

 an external origin, being the outgrowth of 

 the epidermis (including part of the im- 

 mediately subjacent region) of that part 

 of the stem which is situated over a 

 developing root. 



Such a structure as this evidently falls 



into the category of " correlative " growths. ^. ^^ ,., ,. ,, 



=* -' *= figure 2o. — (xroup or cells 



Having no immediate organic connection from surf ace of coleorrliiza, 

 with the root and yet taking its inception showing secretion cells. 

 close on the development of that organ, '^ 



the nature of its growth is analogous, for example, to the correlative 

 growth manifested in the development of fruit and fruit-covering 

 after fertilization of the egg cell and during the development of 

 the embr30. 



As to the function of the coleorrhiza in Ruppia, not much can be 

 said with any certainty. Perhaps it acts as an organ of protection 

 for the root until the latter attains some length. The facts that it 

 occurs only in water plants, so far as known ; and that also, borne 

 on it, are abundant secretion cells, ma}' point to a functional secretion 

 of slime of some sort to protect the young root in the water. 

 Goebel (1893, pp. 233-237) has noted this quite general "production 

 of slime and slime-producing organs in water plants and has ex- 

 plained in some detail its beneficial eftects. It has already been 



Trans. Conn. Acad., Vol. XIV. 8 December. 1908. 



