S92 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



Fertilisation of Lichens. 

 Lichen Apothecia, The Formation and Development of some. 



By E. Baur {Flora, vol. Ixxxviii. 1901, pp. 319-332 ; pi. xiv., xv.).— 

 This research was intended to seek, by the method of sections, for light 

 on the alleged fertilisation of Lichens. In all cases examined the 

 .ascogenous hyphae were braced to a carpogone bearing a projecting 

 trichogyne, but no fertilisation was observed ; this does not exclude the 

 ^extreme probability of its occurrence, as in Collema and the Lahoul- 

 heniacece. The species examined were Parmelia Acetabulum, Anaptychia 

 ciliaris, Fhyscia alba, Pertusaria communis, and Pyrcnula nitida. 



M, H. 



Relation of Lime and Magnesia to Growth. 



Lime and Magnesia : Their Relation to Plant Growth. By 



•Oscar Loew and D. W. May {U.S. Dep. Agr. Bur. PL Ind. Bull. i. 1901). 

 Two . papers are printed in this Bulletin, the first, by 0. Loew, dealing 

 with the liming of soils from a physiological standpoint ; and the second, 

 by D. W. May, on the experimental study of the relation of lime and 

 magnesia to plant growth. 



The presence of an excess of magnesia in a soil renders it practically 

 sterile, and the application of lime made from magnesian limestone in 

 the case of certain soils has been found to be damaging to the growth 

 of crops. The author considers that the bad efiects sometimes observed 

 after the addition of kainit and other Stassfurt salts to certain soils are 

 mainly due to the high magnesia content of these artificial manures. 

 These deleterious efiects can be mitigated or completely removed by a 

 dressing of lime or other calcium compounds. 



Loew draws attention to the analysis of numbers of soils from various 

 parts of the world, in regard to the relative amounts of calcium and 

 magnesium in them, and points out that although the ratio of these 

 two constituents varies between wide limits, in all cases of great 

 fertility of the soil there is never a marked excess of magnesia over 

 lime in them. Usually the amount of lime exceeds that of magnesia 

 -considerably. 



For the satisfactory nutrition of plants a certain ratio between these 

 two nutrients produces the best results. 



Loew considers that magnesia serves largely for the assimilation of 

 phosphoric acid, since magnesium phosphate gives up its acid more 

 readily than any other phosphate met with in plants. When lime is 

 taken up in excess it combines chiefly with the phosphoric acid, and the 

 formation of the necessary amount of magnesium phosphate is prevented. 

 The effect will be the same as if there was a diminution of phosphoric 

 acid in the soil, and starvation may set in. 



In water cultures it has been observed that plants growTi in solutions 

 >of magnesium salts soon become unhealthy, but the injury can be pre- 

 vented and removed by the addition of calcium compounds. Similar 

 results have been obtained in the field. 



The experimental work described by May in the second half of the 

 Bulletin was carried out with the object of determining the efiect of vary- 



