912 SUMMARY OF CURRENT RESEARCHES RELATING TO 



are somewhat flattened tangentially, this being most strikingly the 

 case with the layer of cells which immediately surrounds the canal. 

 Both in older and younger canals, portions of non-deliquesced cell- 

 wall are constantly found projecting into them, from which the con- 

 clusion may be drawn that the canals are formed in the young organ 

 at the time of the differentiation of the tissues while they increase in 

 size from the resorption of the surrounding tissue. 



In the youngest recognizable stage of development, the gum-canals 

 have the appearance, on transverse section, of highly refractive 

 spots. Greater magnification distinguishes the separate cells, which 

 contain a strongly refractive substance, the cell-walls being already 

 very transparent. The addition of alcohol shows subsequently masses 

 of gum collected in the cells, the greater part of the cell-walls then 

 deliquescing, although portions still remain. The gum forms at first 

 a homogeneous mass, in which, however, are often imbedded remains 

 of the protoplasm. The adjoining cells have now undergone changes 

 which prepare them for resorption. Coalescence of canals was fre- 

 quently observed, especially in the stipules of Pterosjjermum, large 

 poi'tions of the tissue becoming converted into lacunfe, traversed by a 

 reticulation of isolated rows of cells. 



Rosanoff's Clusters of Crystals.* — According to K. Demeter, 

 these clusters of crystals occur in Boehneria hiloha, B.japonica, Leuco- 

 syhe candidissima, Mercurialis hirta S heterocarpa, Elatostema eurkyn- 

 cJium, and most beautifully in Boehmeria celebica and Debregeasia 

 dicJiotoma, all belonging to the Urticacege. 



The pith of Boehmeria celebica consists of large, thick-walled, 

 polyhedral, pitted parenchymatous cells, between which lie more 

 elongated cells, of smaller diameter, parallel to the axis of the 

 stem. These contain the largest number of Eosanoflf's clusters of 

 crystals, attached to ridges of cellulose, the number, direction, and 

 strength of which are variable. They may occur in considerable 

 numbers, but are seldom altogether wanting. Their breadth is in 

 inverse proportion to their length, and they are often tubular. Their 

 chemical nature is similar to that of cellulose ; usually they are some- 

 what lignified, like the walls of the medullary parenchyma. Where 

 the clusters are small, these ridges are expanded like a funnel at the 

 spot where they pass over into the cellulose envelope of the clusters. 

 These ridges of cellulose are sometimes found without any clusters of 

 crystals, and in cases which exclude the possibility of any having 

 fallen off. 



Assimilatingf Tissue of Few-leaved Plants.f — H. Pick has in- 

 vestigated the anatomical structure of the tissue of plants with but 

 few leaves, especially species of Casuarina, Ephedra, and Spartium, 

 the leafless species of Acacia, Asparagus, Buscus, and Phyllanthus, 

 Papilionaceae, thorny forms of Colletia, Muhlenbechia platyclados, and 



* ' Magvar noventyani Lapok,' v. (1881) p. 33. SeeBot. Centralbl., vi. (1881) 

 p. 341. 



t Pick, H., ' Beitrage zur Kenntniss der assimilirendeu Gewebes armlaubiger 

 Pflanzen,' Inaug. -Dissert., 34 pp., Bonn, 1881. 



