1430 AGRICULTURAL BOTANY, CHEMISTRY AND PHYSIOLOGY OF PLANTS 



but that this ceased after the first few appHcations of salts. Stem deve- 

 lopment both as regards length and thickness was retarded, biit the lower 

 internodes were not shortened to the same extent as the upper ones, pro- 

 bably owing to the fact that the plant was less imhealthy in the early than 

 in the later stages of its life. Raphanus stems were less straight, the an- 

 gles were more marked at the point of attachment of each leaf. As a rule 

 flowering and side branches behaved exactly like the main stem, but 

 in Phaseolus the branches were larger in proportion. In all cases both 

 stem and branches were greener than in control plants. The time ot flower- 

 ing varied v/ith different plants, the flowers being always dwarfed. 



While the development of the lower leaves was usually normal, the 

 growth of the upper ones was poor. Leaf blades and petioles were affec- 

 ted, leaf blades being frequently bent and twisted. The leaves were also 

 darker green in the initial stages, but this difference gradually faded 

 away. .Stomates were smaller than in normal plants. The root s^'stem 

 was stunted by large doses of mineral salts. 



Anatomical examination revealed the following differences between 

 normal and injured plants : In the stem, the cortex cells were smaller ; 

 the chlorophyll content was higher ; the formation of starch, tannin and 

 oxalate was less active. In the leaves the same dift'erences were observed; 

 the leaf-blades were also thicker and while the smaller size of all cells was 

 noticeable it was especially marked in the epidermis and in the palissade 

 tissue. Raphanus besides containing more chlorophyll also had larger chro- 

 mophores. 



In a small number of trials, the pots were lixiviated after a certain 

 time to remove the excess of salt and the plants were allowed to develop 

 under normal conditions. Recovery occured in direct ' proportion to the 

 am_ount of injury which the plant had suft'ered. 



1068 - Nitrogen Requirements of the Olive Tree. — Petri, l in -^tti dcUa Rcaie Accadcmia 



Economica Agraiia dci Gcorgolili di Fircnzc, Vol. XCLV, pp. 138- 14-. Florence, JulV; 1916 



The writer has shown in previous investigations on Olea europea {1. 

 that all members of that species, wild or cultivated, growing on poor or rich 

 soil, invariably bear a certain number of flowers in which the ovary is not 

 completely differentiated and that imperfect flowers such as these fail 

 to fruit. In normal plants the cause of the abortion lies with the supply 

 of nitrogenous substances in the flowering branches which is not sufficient 

 to meet the requirements of all the flowers produced. Lack of soil moisture 

 is also an indirect cause, for by injuring both roots and leaves, it interferes 

 with the transpiration current and thus prevents the transport of sufficient 

 nitrates to the flowering branches for the proper develo]oraent of all ovaries. 

 The difference between the nitrogen content of a perfectly fertile branch 

 and that of one bearing nothing but flowers with abortive ovaries has 

 proved to be considerable ; while the former was shown to contain from 



(i) Petri L- Studi suUe jiialaltic dell'ulivo. V. Ricerche .<iilla biologia c patologia del- 

 I'olivo. Memcria della R. Slazione di Patolog,ia vei^ctalc, V, pp. 5-64. Ronin, 1914. See also 5. 

 1915, No. loS. 



