Germination of Grass-Fruits. 203 



Alopecurus pratensis, and A. agrestis, and the lemma of Oryza 

 sativa, — the writer has not observed a splitting of the fibrovas- 

 cular bundle, at germination. The separation of the fibrovas- 

 cular bundle from the parenchyma may be observed very dis- 

 tinctly in Phalaris arundinacea and Phalaris canariensis. Here 

 two types of cleavage may occur. The coleorhiza may, like in 

 Alopecurus, either cause a slit which is continued along the 

 fibrovascular bundle, or, the median fibrovascular bundle may 

 be ruptured at the base of the lemma and separated from the 

 latter by two parallel longitudinal slits running along its sides. 

 With Alopecurus the tissue at the base is not ruptured at germi- 

 nation probably on account of the flattened, spatula-like shape 

 of the coleorhiza whose pressure is directed against only a nar- 

 row zone, in the plane of the median vascular bundle. 



The penetration of the coleorhiza through the powerful 

 obstacle presented by the lemma would require such a consider- 

 able effort that one must assume the presence of certain arrange- 

 ments in the structure of the lemma, tending to reduce its resis- 

 tance and facilitate the task of the coleorhiza. An investigation 

 into the tissues of the lemma revealed a very marked differentia- 

 tion and reduction of the tissues in the basal region of the 

 lemma. 



Considering first the tissues of the lemma of Loliiim itali- 

 cum, it will be seen that the epidermis, throughout the greater 

 part of the lemma is built with a view to mechanical firmness 

 (Fig. 33.)- Towards the base, however, the jagged processes of 

 the longitudinal walls of the epidermal cells decrease and ulti- 

 mately disappear, the walls assuming a wavy aspect. The sili- 

 cious cells likewise disappear so that here the contiguous epi- 

 dermal cells touch each other directly with their septae. In the 

 proximity of the base of the lemma the epidermal cells become 

 thin-walled, their longitudinal and transverse diameter decrease 

 and finally they assume the aspect illustrated in Fig. 34 (upper 

 part). A comparison of Fig. 33 with Fig. 34 will afford suffi- 

 cient evidence of the changes in the epidermal cells. After 

 forming the transverse basal groove the epidermal cells enter 

 the basal callus. 



The callus presents a very interesting anatomical detail. 

 With Lolium italicum it has a flat semi-globular form, and over 

 its upper edge extend the above-named super-basal cells of the 



