82 SUMMARY OF CURRENT RESEARCHES RELATING TO 



(3) Structure of Tissues. 



Literal Plants.* — Herr C. Bricl? finds tlie general characteristics of 

 literal halophilous plants to be a succulent tissue in the form of a strongly 

 developed cortical parenchyma ; the invariable presence of a vascular 

 bundle-sheath, which serves as a starch-sheath ; and the rarity of starch 

 in the chlorophyll- grains. The strong turgidity of thG cells may be due 

 to the formation of salts of an organic acid with the soda with which 

 they are so abundantly supplied, 



Herr Brick proposes the following types of halophilous plants : — 

 (1) The cortical parenchyma is composed, of roxmd cells, between which 

 are small triangular or polygonal intercellular spaces ; the chlorophyll 

 is either distributed through the parenchyma, or is limited to a special 

 outer zone of the cortex {Honckenya peploides, CaMle maritima). (2) The 

 cortical parenchyma consists of round cells, between which are large 

 nearly regular air-passages (^Aster Tripolium, Glaux maritima). (3) The 

 cortical parenchyma has a structure similar to that of a leaf ; the chloro- 

 phyll is usually confined to the palisade-cells (Salsola Kali, Salicornia 

 herhacea). 



Comparative Anatomy of Desert Plants.f — M. P. Maury has 

 examined the structure of a large number of species of flowering plants 

 from the Algerian Sahara, and finds them characterized in common by 

 the following features : — But slight thictening of the epidermal walls ; 

 the epidermis similar on the two faces of the leaf ; the hypoderm con- 

 sisting of a single layer of cells ; the cortical parenchyma partly of a 

 palisade nature, or simply assimilating ; the pericycle with sclerotized 

 elements ; the vessels of the root with a larger diameter than those of the 

 stem ; a palisade-parenchyma on both faces of the leaf ; the median 

 parenchyma uncoloured, with gummy cells ; ramifications of the vessels 

 in the horizontal plane of the leaf not provided with sclerotized 

 strengthening elements. In no case do these features conceal the special 

 characters of the genus or family, but serve to adapt the species to its 

 peculiar conditions of life. 



Palisade-parenchyme.f — From observations made on both water and 

 land plants, Herr 0. Eberdt concludes that the chief factor in determin- 

 ing the formation of palisade-parenchyme in leaves is not light, but 

 strong transpiration and the rapid transport of formative substances. 

 Diminished transpiration, even when there is strong assimilation, causes 

 directly a disruption of the palisade-parenchyme ; its cells become much 

 less closely fitted together, intercellular spaces appearing between them. 



Stem of Ephedra.§ — Mr. W. H. Evans points out that, according to 

 Bentham and Hooker, Ephedra occupies an intermediate position between 

 WelwitscJiia and Gnetum in the order Gnetacese. Holding thus a low 

 rank among Gymnosperms, we would expect interesting anatomical 

 structure. In all there are about thirty species, most of which are 



* Schrift. Naturf. Gesell. Danzig, vii. (1888) pp. 108-15. See Naturforscher, xxi. 

 (1888) p. 214. 



t Assoc. Fran9. pour Tavance. d. sci., Cougres de Toulouse, 1887. See Morot's 

 Journ. de Bot., ii. (1888) Kev. Bibl., p. 101. 



X ' Beitr. zu d. Unters. ub. d. Entstehungsweise des Pallisaden-parenchyms,' 

 Freiburg-i.-B., 1887, 52 pp. See Bot. Centralbl., xxxv. (1888) p. 362. 



§ Bot. Gazette, xiii. (1888) pp. 265-8. 



