474 SUMMARY OF CURRENT RESEARCHES RELATING TO 



plants, and deduces the conclusion that vernation, conduplication, 

 the various positions taken up by developing leaves, &c., all conspire 

 to protect them from the evil effects of radiation. 



Anatomy and Morphology of submerged Monocotyledons.* — 

 M. T. Holm gives a detailed description of the structure of two sub- 

 merged species of Monocotyledons, Halophila Baillonii, a marine 

 plant, and Elodea densa, from Brazil. 



Leaves of Sagittaria.f — According to M. J. Costantin, the two 

 forms of leaf of Sagittaria sagittsefolia are not the result of external 

 conditions, and do not pass the one into the other, but are distinct 

 from the bud-condition. The ribbon- shaped leaves undergo great 

 change when they come into contact with the air, only then developing 

 stomata and palisade-tissue. When the plant grows at a great depth 

 in the water, it has not sufficient vitality to produce the arrow-shaped 

 leaves, and does not flower. 



Anatomy of the Leaves of Aroidese-I — The examination of a 

 large number of species of Aroidese leads Dr. M. Dalitzsch to the 

 conclusion that the anatomical structure of the leaves affords cha- 

 racters for their systematic classification, derived from the presence 

 or absence of intercellular sclerenchymatous fibres, the presence or 

 absence of laticiferous tubes, and from the form in which the oxalate 

 of lime is deposited in the cells. The leaves of Spathiphyllum, BhapJii- 

 dophora, Monstera, and Scindapsus have intercellular sclerenchyma- 

 fibres, but no latex-tubes ; the remaining genera have latex-tubes, but 

 not the intercellular fibres. Eaphides-cells are especially abundant 

 in Colocasia. Amorphophallus and Acorus have no crystals ; the latter 

 abounds in resin-cells. Large intercellular spaces are wanting only 

 in AntJiurium, Monstera, SpatMpTiyllum, and Scindapsus, which grow on 

 rocks, or epiphytically on trees ; they occur in the epiphytic Philo- 

 dendra, but are filled, not with air, but with a very thin mucilage, 

 often containing tannin. The red and yellow dots which occur 

 especially on the under side of the leaf of many species of Anthurium 

 are glands, the secretion being formed between the cuticle and the 

 epidermal membrane. 



Closing of the Scar after the Fall of the Leaf.§ — According to 

 Herr L. Staby, the healing of the wound after the fall of the leaf 

 takes place in four different ways, viz. : — 1, By drying up of the 

 surface of the wound (tree-ferns) ; 2. By the formation of reticulated 

 cells (Orchideae) ; 3. By the formation of periderm ; this is much the 

 most common mode ; 4. By temporary closing by gum ; this is also 

 very common. 



* Bih. K. Svenska Vet6ns.-Akad. Handl., ix. (1885) (4 pis.). See Bot. 

 Contralbl., xxv. (1886) p. 6. 



t Bull. Soc. Bot. France, xxxii. (1885) pp. 218-23. 



% Bot. Centralbl., xxv. (1886) pp. 153-6, 184-7, 217-9, 249-53, 280-5, 312-8, 

 343-9 (1 pi.). 



§ Staby, L., ' TJeb. d. Vevschluss der Blattnarben nach Abfall d. Blatter,' 

 39 pp., Berlin, 1885. See Bot. Centralbl., xxv. (1886) p. 38. 



