206 Maine Agricultural Experiment Station. 1920. 



chyma gradually increases, attaining its greatest extention near 

 the marginal bundle. Thus the parenchyma predominates in the 

 region between the lateral and marginal vascular bundles and as 

 a result the tissue of the lemma of Festuca arnndinacea and other 

 grasses is ruptured by the coleorhiza between these two fibrovas- 

 cular bundles. 



The very remarkable aspect which the tissues of the lemma 

 assume above the line of rupture is illustrated in Fig. 38 which 

 represents a section between the lateral and marginal fibrovas- 

 cular bundles, corresponding to the one given in Fig. 37 (around 

 the median bundle.) A comparison of Fig. 38 with Fig. 37 shows 

 the powerful development of the epidermis and prosenchyma 

 composed here of strongly thickened cells possessing a small 

 lumen. On the other hand, the parenchyma is reduced to two or 

 at the most, near the vascular bundles, to three cell layers. The 

 cells of the inner epidermis possess a small lumen and are com- 

 pressed transversely. 



The conditions found in Lolium italicum and Festuca arun- 

 dinacea are typical of the other grasses. 



Having described the nature of the tissue at the base of the 

 lemma it will now be of interest to discuss the manner in which 

 these tissues are affected by the penetrating coleorhiza of the 

 germinating embryo. Under the pressure of the coleorhiza the 

 thin-walled cells of the inner epidermis and the parenchyma are 

 stripped off and frequently distorted. Next the coleorhiza strikes 

 upon the prosenchymatous tissue. Under its pressure the cells of 

 the prosenchyma are moved apart along the line of juncture of 

 the long sclerenchymatous and the short cells of the base, there 

 occurring no injury to the cells. As illustrated in Fig. 35 B this 

 line runs along the oblique or transversal septae of the scleren- 

 chymatous cells which remain completely intact. The spaces 

 between the projecting ends of these cells were originally occu- 

 pied by the short cells of the base of the lemma. Occasionally a 

 few of these short basal cells adhere to the sclerenchymatous 

 cells after the coleorhiza has broken through. (Fig. 35B, bb.) 



The cells of the outer epidermis behave in a similar manner. 

 Here the separation of tissues occurs along a line at which two 

 series of cells differing as to form and physical characteristics 

 meet, the thin-walled, almost transversely lying cells of the 



