STORAGE TISSUES OF THALLOPHYTA 431 



the central strand of conducting elements. This storage-tissue consists 

 of numerous layers of relatively large isodiametric cells, with more or 

 less thickened and pitted walls ; the limiting membranes of the pits 

 are traversed by tine perforations. 



In the case of Fucus serratus, the contents of these cells consist, 

 according to Hansteen, of granular masses of a special carbohydrate 

 substance, which he terms fucosan. In Dictyofa dichotoma, the storage- 

 tissue is represented by the central or medullary layer ; this tissue 

 consists of a single layer of cells in the flattened portions of the thallus, 

 but is many-layered in the cylindrical stem-like region. According to 

 Hansen, each storage-cell contains a group of large oil-drops suspended 

 in a central mass of cytoplasm, from which a number of protoplasmic 

 strands radiate towards the cell-wall. The depletion of the storage- 

 tissue which takes place in connection with the production of adventi- 

 tious shoots or reproductive organs, is preceded by emulsifieation of the 

 large oil-drops. 



Genuine water-tissues seem also to be unknown among the Fungi, 

 unless the large vesicular cystidia that occur in the hymenium in certain 

 Hymenomycetes (e.g. spp. of Goprimts), serve as reservoirs of water, 

 besides performing the mechanical function attributed to them by 

 Brefeld and Von Wettstein [and also by Buller] of keeping the gills 

 apart while the spores are being liberated. The sclerotia of Fungi are 

 always provided with typical storage-tissues for plastic materials, in the 

 shape of a medullary region, composed either of closely interwoven 

 tubular hyphae or of pseudo-parenchyma (plectenchyma). The non- 

 nitrogenous reserve-materials consist of greatly thickened gelatinous 

 cell-membranes or of masses of fat, and are accompanied by varying 

 quantities of protein-compounds. The depletion of these sclerotial 

 storage-tissues, in connection with the development of fruit-bodies, 

 closely resembles the corresponding processes in Higher Plants. In 

 the case of Clavicepis purpurea, for example, the fat disappears com- 

 pletely, and the thickened cell-membranes are also largely used up. 

 Finally, it may be mentioned that, according to Errera, glycogen, a 

 polysaccharide closely related to the dextrines, which is widely dis- 

 tributed in the animal kingdom, also frequently occurs in large quan- 

 tities both in the higher and in the lower Fungi, and probably always 

 represents a reserve-material. 



Protein-substance (? protoplasm) is stored for ecological reasons by 

 a Southern P>razilian Agaric, Rozites gongylophora, in terminal swellings 

 of special hyphae ; according to Moller, these " Kohl-rabi-clumps " are 

 devoured by the Leaf-cutter Ants which cultivate this Fungus in their 

 nests. 206 



