78 SUMMARY OF CURRENT RESEARCHES RELATING TO 



parenchyma. The special development of the leaf is described in a 

 number of individual cases. The largo air-cavities may be either 

 schizogenous or lysigenous. 



The mechanical system of the whole plant is reduced to a very feeble 

 development. Organs for secretion and excretion are, as a rule, entirely 

 wanting, though calcium oxalate is sometimes excreted abundantly. 

 The root-system of submerged plants seldom attains any great develop- 

 ment. The central vascular cylinder is probably formed from the 

 union of a number of bundles. 



Lateralness in Coniferae.* — The term " lateralness " of an organ is 

 defined by Herr E. Henning as expressing the distribution of the 

 phenomena of organization on the transverse section, or especially 

 around the axis of growth. Strictly speaking, all the leaves of conifers 

 arc dorsiventral, since the vascular bundles are collateral. He describes 

 the lateralness of a leaf as radiar when the tissues are uniformly 

 developed around the vascular bundle, and if the leaf has, in addition, a 

 circular or polygonal transverse section ; bilateral when they are flat 

 while the structure of the tissue is the same. A table is given of the 

 variations, within the order of Conifera?, of the combinations of these 

 and some other differences of structure connected with the lateralness of 

 the leaves and branches. 



Dichotypy.f — Herr W. 0. Focke adduces the following instances of 

 dichotypy, i. e. of the occurrence of two different forms of the same 

 organ on the same stock : — A number of specimens of a hybrid between 

 Anagallis phoenica and A. cserulea, in which most of the flowers were 

 scarlet, a single one having half one of the corolla-lobes dark blue ; a 

 specimen of Mirabilis Jalapa, in which most of the shoots had white 

 flowers sprinkled with red, a few pure red flowers; and a hybrid 

 between Trollius europeeus and T. asiaticus, in which most of the flowers 

 were yellow, those on a single branch red. 



Flowers and Fruit of Sparganium and Typha.J — This treatise by 

 Dr. S. Dietz is now published in detail, with illustrations. The two 

 genera should, he considers, be placed under distinct families, or at 

 least sub-families, Sparganinm having a nearer affinity to the Panda- 

 nacese, Typlia to the Aroidese. The fruit of Typlia is a caryopsis, that 

 of Sparganium a drupe. 



Fruits and Seeds of Rhamnus.§ — Prof. H. Marshall Ward (assisted 

 by Mr. J. Dunlop) has conducted a series of experiments for the purpose 

 of explaining the phenomena connected with the colouring matter of 

 species of Hhamnus, especially B. infectorius. A beautiful golden 

 yellow solution can be obtained by macerating the fruit in water ; but, 

 although the seat of the pigment is evidently the pericarp, the whole 

 berry, including the seed, must be crushed in order to obtain it. The 

 explanation of this phenomenon offered by Prof. Ward is that the 

 xanthorhamnin present in the pericarp is a glucoside, and that it breaks 

 up, under the influence of a ferment present in the seed, into the 



* Naturv. Studentsallsk. Upsala,' Feb. 24, 1887. See Bot. Centralbl., xxxi. 

 (1887) p. 393. 



t Abhandl. Naturwiss. Ver. Bremen, ix. (1887). See Bot. Centralbl., xxxii. 

 (1887) p. 43. 



X Uhlworm und Haenlein's Bibliotb. Bot., v. (1887) pp. 1-59 (3 pis.). Cf. this 

 Journal, 1887, p. 114. § Ann. of Bot., i. (1887) pp. 1-26 (2 pis.). 



