260 JOURNAL OF THE 110 YAL HORTICULTURAL SOCIETY. 



Berthollctia, described by Mr. Watson in the " Annals of Botany," is also 

 alluded to in this connection. — R. I. L. 



Mycorhizoid Structures. 



Mycorhizoid Structures in Marchantiaceae. By M. Golenkin 

 {Flora, xc. 1902, pp. 209-220; pi. 11).— This occurs in Marchantia 

 palmata, M. paleacea, Preissia commutata, Fegatella conica, Targionia 

 hypophylla, Plagiochasma clongatum (from Java) ; but not in Mar- 

 chantia polymorpha, Lunularia, nor eighteen other species, including 

 Bicciece. It is " endotrophic," and forms in Preissia and MarcJiantia 

 two dark violet cords of oval section, one on either side of the central 

 groove, respecting the lower epiderm and the branching green cells. 

 The distribution differs in the other species. The affected cells are 

 traversed by numerous hyphae, and never contain starch or chloroplasts, 

 though they retain protoplasm and nucleus. The hyphai grow through 

 the cells of the non-lacunar tissue, infecting the youngest ones about 

 5 mm. from the growing point. None enter the air chambers, and the 

 stalk of the inflorescence also escapes infection. 



Attempts to cultivate Preissia and Fegatella species from bulbols and 

 spores on sterilised earth gave w T eakly plants (soon killed by parasitic 

 fungi), or none. The strongest wild specimens producing female fruit 

 were always infected. The Mar chant ias, however, were in some cases 

 free from mycorhiza and yet flourished, though they gave no inflores- 

 cences ; this, however, frequently occurs in cultures. [The description 

 of these observations and experiments is lacking in detail ; thus we find 

 no account of " control experiments " on Preissia and Fegatella in ordinary 

 soil.] It is suggested that the function of the mycorhiza is to resist drought. 

 The fungus could not be identified. It is compared with the symbiotic 

 fungi of Neottia to the prothallus of Lycopodium. — M. H. 



Secretion in Nectaries. 



Nectaries, Mechanism of Secretion in Extra-floral. By 



Haupt Hugo (Flora, vol. xc. 1902, pp. 1-41). — A very interesting account 

 of these organs studied in a limited number of European plants. Secre- 

 tion commences automatically at a certain age and when the air is 

 sufficiently moist ; its continuance depends partly on the presence of the 

 excreted sugar becoming concentrated and exercising osmotic attraction. 

 But as the removal of the nectar does not invariably (as hitherto believed) 

 arrest the secretion, the starting mechanism must be renewed. In other 

 cases the removal of the nectar is followed by a secretion of mere water, 

 the nectary thus becoming a water-gland (hydathode). This proves that 

 the secretion is in part due to internal pressure. In some few cases only 

 (Vicia, Euphorbia) light — the less refrangible rays — has a direct influence 

 on the secretion, as well as an indirect one through the illumination of 

 other parts of the plant. Secretion never begins below a minimum 

 temperature proper to the plant, though already active nectaries will 

 continue to secrete more slowly when the temperature falls below this. 

 The arrest of the secretion with the age of the organ is sometimes accom- 

 panied even by resorption of the nectar ; in Vicia and Euphorbia darken- 

 ing alone will determine this. Nectaries capable of absorbing their own 



