4 



The Natukaltst. 



ieafy stems from the surface. Tetradontium and Tttrapfds also produce 

 a flat pro-embryo at the end of the filaments of a protonema. Kiihn's 

 investigations on Andreoea show that it also differs from the typical 

 mosses, as the contents of the spore divide into four or more cells 

 before bursting. This observer has also shown that the first septum 

 of the protonema is formed within the spore in the true mosses, as 

 Mnium, Lemobryim^ Hypmm, and Bartramia. The branches of the 

 protonema of Andreoea may produce cellular ribbons as well as trans- 

 verse and longitudinal divisions, and parallel to the surface of these 

 divisions other divisions may be formed, and an aborescent erect 

 portion of the protonema may result, but sometimes a single plate of 

 tissue having a definite .outline is the result. The length of the 

 protonema varies from 1 m.m. to 300 m.m. The length of a moss 

 varies from 1 m.m. to over 300 m.m., but the thickness does not vary 

 more than from m.m. to 1 m.m. The leaf-bearing plant springs 

 from the lower cells of the lateral branches of the protonema, and 

 never from the apical cell of a filament of the latter. From the first 

 leaf-forming segments arise the first rhizoids. I might here have 

 gone into the manner in which the branching of the stem originates, 

 but I must be content with saying that the branching is never dicho- 

 tomous, and probably never axillary, although connected with the 

 leaves. The leaf-tissue of Sphagnum and Leucobryum is differentiated 

 into cells of definite position, some containing sap, and some air. 

 The stolons of mosses are shoots with none or very small leaves ; 

 they creep on or beneath the surface of the soil and then erect them- 

 selves as leafy shoots. The lamina expands right and left from the 

 median plane, except in Fissidens, and here it is expanded in the 

 median plane itself, proceeding from an almost sheathing base. The 

 rhizoids or root-hairs are plentifully developed except in Sphagnum, 

 and are not morphologically distinct from the protonema ; they 

 certainly do not contain chlorophyll, and they likewise tend to grow 

 downwards, but they sometimes develop single branches as a proto- 

 nema growing upwards, and the protonema also develops rhizoids. 

 To cause the protonema to be developed from the rhizoids, keep a 

 turf of moss turned upside down and damp for a few days, when 

 protonema will be developed, bearing plants in abundance. 



Wo h ave seen that the usual method of reproduction is by means of 

 the spores of the sporogonium, which sporogonium was proved to be 

 equivalent to the entire leafy and rooting spore-producing plant of vas- 

 vascular cryptogams, in 1851, by Hoflmeister, and is one of the finest 

 revelations ever made in morphology and classification. The protonema 



