PROTOPLASM. 



[ 540 ] 



PSILOTUM. 



spores in course of division appears like a 

 varicose tube ; it is septate, however, and 

 when the globular spores are mature, they 

 have a double coat ; in P. macrosporus, the 

 diameter of the ripe spore is about 1-5000". 

 When advanced in age, the mycelium appears 

 to be wholly converted into spores, which 

 become free. The existence of these Fungi 

 is rendered more or less evident externally 

 by warty projections of the epidermis, finally 

 bursting, linger describes four species : P. 

 macrosporus occurring on CEaopodium and 

 Angelica ; P. endogenus (Galii) occurring on 

 Galium mollugo ; P. microsporus on Ranun- 

 culus repens ; and P. Paridis on Paris qua- 

 drifolia. De Bary found a species on Me- 

 nyanthes, with oval spores 1-800" long and 

 1-1300" broad. 



BIBL. linger, Exanthem. der Pflanz. 

 p. 341 ; De Bary, Erandpilze, p. 15. pis. 1 

 & 2 ; Leveille, Ann. des So. nat. 3 ser. viii. 

 p. 374; Tulasne, ibid. vii. p. 112; Fries, 

 Summa Veg. p. 517. 



PROTOPLASM. The name applied by 

 Mohl to the colourless or yellowish, smooth 

 or granular viscid substance, of nitrogenous 

 constitution, which constitutes the formative 

 substance in the contents of vegetable cells, 

 in the condition of gelatinous strata, reticu- 

 lated threads and nuclear aggregations, &c. 

 It is the same substance as that formerly 

 termed by the Germans " schleim" which 

 was usually translated in English works by 

 "mucus" or "mucilage" (see PRIMORDIAL 

 UTRICLE, and CELL, VEGETABLE). 



PROTOZOA. This term was proposed 

 by Siebold to designate a group of inverte- 

 brate animals, characterized by the various 

 systems of organs not being distinctly sepa- 

 rated, and their form and simple organiza- 

 tion being reducible to a cell. 



We have applied the term to an order of 

 the Animal kingdom, and somewhat extended 

 its limits (p. 42). Siebold included in it the 

 Infusoria and the Rhizopoda, the latter con- 

 sisting of the Amcebaea, Arcellina and Fora- 

 minifera. 



If the above definition be adopted, it must 

 be remembered that the cell may be repre- 

 sented by the cell-contents only, and these 

 we believe to constitute the essential part of 

 a cell. 



BIBL. Siebold, Vergleich. Anat. iii. 



PSILONIA, Fr. A genus of Sepedoniei 

 (Hyphomycetous Fungi), consisting of little 

 compact tufts of twisted filaments, at first 

 covering the fusiform, globose, or oval spores, 

 which arise from the wart-like protuberances 



on the central filaments, and soon become 

 free. They are found on dead wood or on 

 reeds. 



BIBL. Berk. Brit. Flora, ii. pt. 2. p. 353, 

 Ann. Nat. Hist. ser. 2. viii. p. 179; Fries, 

 Summa Veget. p. 495. 



PSILOTE^E. A family of Lycopodia- 

 ceous plants, distinguished by their many- 

 celled sporanges, varying much in habit and 

 external appearance. 



Synopsis of Genera. 



I. PSILOTUM. Sporanges sessile, three- 

 celled, bursting imperfectly into three valves 

 by a vertical crack, filled with mealy spores. 



II. TMESIPTERIS. Sporanges sessile, 

 three-celled, bursting imperfectly into two 

 valves by a vertical crack, filled with mealy 

 spores, 



III. ISOETES. Sporanges imbedded in 

 the bases of the leaves, and adnate at the 

 back, not valvate, with several transverse 

 septa; containing two kinds of spores (in 

 distinct sporangia). 



PSILOTUM, Swartz. (Lycopodium nu- 

 dum, L.). An exotic genus of Psilotese (Ly- 



Fig. 615. 



Psilotum triquetrum. 

 Nat, size. 



