230 BOHDAN SLAViK 



intensity at the leaf base being i2-o mg COa/dm^hr) is statistically very 

 significant (P^ o-ooooooi). (See Table i.) 



If the differences in the intensity of photosynthesis are to be compared 

 with the different tissue hydration expressed as osmotic pressure of the cell 

 sap, i.e. if the differences are to be compared with the plasma factors of 

 photosynthesis it must be known to what extent our results could be 

 influenced by a different factor, viz. by the stomata, possible differences in 

 their density, size and state. The results of these estimations are shown in 

 Table 2. 



Table 2 

 Number aiid size of stomata and relative index of pore area 



Leaf-blade apex Leaf-blade base 



_A , , A_ 



Upper side Lower side Upper side Lower side 

 Number of stomata 



per mm^ 66-3 ±0-70 82-9±o-75 110-3 ±1-54 i46-9±,-59 



Size of stomata (length of 



pore in/i) 30-8 + 0-21 29-6±o-25 23-7+ 0-23 23-1 ±0-26 



Relative index of total 63-3 72-5 61*5 77-8 



pore area 



V ^ / V ^_ 



135-0 139-3 



While the number of stomata on the upper and lower side of the leaf- 

 blade is significantly greater at the base, the length of the pores is statisti- 

 cally greater in the stomata from the apical part. In order to calculate the 

 relative index of the true pore area a simphfying assumption must be 

 employed, namely that all stomata have the same relative shape or in other 

 words, the same ratio of length to width of pore at the given extent of 

 opening all over the leaf-blade area. As the pore area is proportional to the 

 square of its length, the product of the number and square of pore length 

 may be taken as the relative index of pore area. Indexes derived in such way 

 (as shown in Table i) indicate that the total area of pores at the base and at 

 the apex differs by 2-5 per cent only, in spite of the above contradictory 

 differences in number and size. 



Statistical significance of this difference was not tested on account of 

 the very laborious calculation of the index separately for each field of vision. 

 But even if the difference is statistically significant it is insufficient in 



