Germination of Grass-Fruits. 205 



marginal fibrovascular bundles in the lower region of the lemma, 

 the prosenchyma forms a strong layer of mechanical cells, which 

 enter the base and penetrate it transversely. A part of them 

 resolve themselves about the middle of the base into short cells. 

 while most of them connect with the tissues of the rachilla bear- 

 ing the upper spikelet. This rachilla has a pillar-like form com- 

 posed of long, pitted, cells which terminate at the apex with a 

 ring of short cells upon which the base of the upper spikelet 

 rests. Towards its lower end the rachilla broadens and enters 

 the base of the lemma of the lower spikelet. Its central tissue 

 runs out into small cells while the lateral cell layers on entering 

 the base of the lemma of the lower spikelet turn outwards, be- 

 come short-celled, and join the lateral layers of the base referred 

 to above. The point of juncture of these two cords of tissues af- 

 fords a very interesting mechanica detail. Here peculiar knee- 

 shaped cells are found which penetrate with their pointed ends 

 into the intercellular spaces of the two tissue-cords thus estab- 

 lishing a joint btween the base of the lemma of the lower and 

 the rachilla of the upper spikelet. This hinge-like detail enables 

 the lemma to execute a turning movement at the time of bloom. 



To complete the description of the base of the lemma it 

 may be added that here we find the point of junction of the 

 fibrovascular bundles. The three fibrovasculat cords on entering 

 the base branch out, five bundles entering the lemma while the 

 remainder goes off to the upper rachilla and palet. 



The changes in the epidermis and prosenchyma occuring at 

 the base of the lemma can also be studied on transverse sections. 

 (See Figs. 36, 37, 38). Fig. 36 represents a section below the point 

 at which the coleorhiza breaks through, showing the thick-walled, 

 pitted cells of the outer epidermis and the likewise thick-walled 

 cells of the prosenchyma. Fig. 37, illustrates a cross-section of 

 the base of Festuca arundinacea, about the line of rupture. Here 

 a remarkable differentiation in the direction of the transverse axis 

 can be noticed. The cells of the prosenchyma to the right of the 

 lateral fibrovascular bundle, towards the median bundle, become 

 thick-walled and finally assume a sclerenchymatous aspect while 

 towards the marginal nerve they possess thin walls and differ 

 little from the parenchymatous tissue. The latter decreases to- 

 wards the median bundle and finally becomes reduced to 2 layers. 

 From the lateral fibrovascular bundle to the marginal the paren- 



