Germination of Grass-Fruits. 213 



coleoptile. Under the pressure of the epiblast the median vein 

 or fibrovascular bundle yields, and in the narrow elliptical open- 

 ing appear the coleoptile and the tip of the epiblast. This aper- 

 ture extends downward, and the coleoptile shows several mili- 

 meters outside the glumes when the coleorhiza appears. Thus 

 with Oryza sativa the coleorhiza and the coleoptile escape 

 through the same opening. 



III. The Mechanical and Biological Function of the 



Coleorhiza. 



A brief description of the structure of the coleorhiza may 

 serve to understand its functions. 



The coleorhiza has the shape of a truncate cone. Its tissues 

 consist of a mass of uniform cells covered by an epidermis ex- 

 tending to the apex of the coleorhiza. The form of the cells 

 varies according to the stage of elongation of the coleorhiza. 

 After the coleorhiza breaks through the glumes its cells appear 

 in the middle section longitudinally extended, utricular, becom- 

 ing shorter in the proximity of the apex terminating by thick- 

 ened cells of the apical appendage. (Figs. 41 and 42). 



The function of the coleorhiza is primarily mechanical in 

 that it breaks the way for the radicle. It acts also as a protect- 

 ing organ for the radicle. Nor is its function over with the 

 penetration through the tissues of the glume. Soon after the 

 coleorhiza breaks through the glume it sends out numerous tri- 

 chomes or hairs whose length depends upon the grass species 

 and the stage of gemination. These trichomes attain their 

 greatest length at time when the radicle comes in contact with 

 the soil or other substratum. 



The trichomes act as fastening organs clinging to the par- 

 ticles of soil or other substratum, thus anchoring the germinating 

 fruit. 



In this investigation trichomes were observed on the coleo- 

 rhiza of the following grasses: Alopecurus pratensis, Alopecurus 

 geniculatus, Alopecurus agrestis, Arrhenatherum elatius, An- 

 thoxanthum adoratum, Anthoxanthum Puelii, Avena pubescens. 

 Bromus Schraderi, Bromus arvensis, Brachypodium sylvaticum. 

 Cynosurus, Dactylis glomerata, Elymus arenarius, Festuca pra- 

 tensis, Festuca ovina, Festuca arundinacea, Festuca heterophylla, 



