NOTES AND ABSTRACTS. 



927 



seed is due to air hollows in the testa. Gentiana hitea and G. Cruciata 

 totally differ in anatomy of the seed. Liitorclla lacustris. — In germina- 

 tion the hypocotyl pushes aside a " plug " formed of the enlarged funicle 

 of the ovule, and then turns towards the earth, in which the very short 

 roots fix themselves. The cotyledons are at first hent and absorb the 

 food material in the seed ; later they bend apart in their lower part, so as 

 to strip off the testa, and then become green. Hairs secreting a mucilage 

 are found on the seedling. Plantago major differs altogether from 

 Littorclla.—G. F. S.-E. 



Water-rats destroying' Trees. By R. Eppner (Nat. Zeit. Land- 

 Forst. i. pp. 404-412, 3 rigs. ; 1903). — In tree nurseries near Munich 

 water-rats have destroyed many trees by gnawing roots and bases of 

 stems. The figures are from photographs of the damage done to Beech, 

 Sycamore, Larch, and Spruce. Various methods of poisoning were tested, 

 but on account of danger to other animals the author prefers traps. Owls 

 are natural enemies of the water-rat. 



In the same periodical (ii. pp. 81-88, 1904) there is a useful paper 

 on the species of Arvicolida (Field-mice, &c), with photographs of the 

 skulls of several species. — W. G. S. 



Water-relation of Puccinia Asparagi. By R. E. Smith (Bot. 

 Gaz. xxxviii. No. 1, p. 19 ; with 21 figs.). — Since 189G this fungus has 

 spread entirely across the continent of America, from Massachusetts to 

 California, with extremely disastrous results to the Asparagus industry. 

 The appearance of the forms varies in extent in different districts. A 

 decided difference in the formation of the disease coincides with the 

 moisture-retaining powers of the soil, " the trouble being worse upon the 

 drier soils," though " it is well established that the development of those 

 fungi that live upon higher plants is favoured by wet weather," and it 

 was " least in wet seasons." " The soil generally is of a high, sandy, dry 

 nature." But the few beds now remaining are almost entirely upon the 

 heavier soils. 



In soils of high water-retaining capacity the teleuto stage alone 

 appeared. In a very dry summer (1897) the uredo stage appeared where 

 never before seen. 



In dry seasons and soils Asparagus has its vitality reduced, and so 

 becomes an easier prey to the fungus. 



With regard to atmospheric moisture, the progress of the fungus was 

 accelerated by excessive dew-fall. Asparagus growing in the shade 

 remains free from rust, while all beyond is dead. This is attributed to 

 the protection from dew. Dew is of absolute necessity in infection by 

 rust, and of more importance than rain. Atmospheric dryness checks 

 fecidial development, the mycelium remaining dormant, and may die out. 

 Uredo is likewise checked, and changes to teleutospores ; but with moisture 

 uredospore formation begins again at once. The teleuto stage is a pro- 

 vision for surviving any condition unfavourable to the fungus. 



With regard to soil moisture, this is of the greatest importance. It 

 retards the development of the fungus by giving the host gi eater vitality 

 and resistance. — G. H. 



