222 



KNOWLEDGE. 



[Deceubeb 1, 1891. 



3fe 



m 



distinction will be readily understood bycompaiing Fig. 1, 

 wliich is a Pleurocarpous Moss, with Figs. "2 and 3, which 

 represent an Acrocarpous 

 ., a. Moss ; in the former it 



yi ,-■' ' will be seen that the axis, 



J ^r or line of growth, is 



iS horizontal, that the 



/ »' c " plant, in short, grows along 



■ /' ,-• ,j the ground, whilst in the 

 Crr/. ^ I (y/ '^' latter the direc- 



tion of growth 

 is vertical. 

 Again, in the 

 former the 

 capsules c c 

 are seen car- 

 ried on stallis 

 originating 

 from the pria- 

 ^^ cipal stem, 



f whilst in Fig. 



2 the capsule 

 W a crowns the 



a line of growth. 



% This dis- 



.|| tinction in the 



mode of carry- 



FlG. 3.— Polytriohum : Hale 

 Plant. After Dillenius. 

 a. Male Blussom. 



ing the capsule is one of 

 great importance in the clas- 

 sification of Mosses, and 

 the student who desires to 

 begin to learn 

 them should pay 

 early attention 

 to it. Often it 

 is perfectly easy 

 of apphcation, 

 but inter- 

 mediate 

 forms oc- 

 cur which 

 are puz- 

 zles, and 

 goto show 

 that the 

 chasm 

 between 

 the two forms 

 over in Nature. 

 Ltfe-Hhtoiy. — I propose now to trace the life-history of 

 a Moss in its most complete com-se of life, and I shall then 

 show how, in many cases, this course is abbreviated. It 

 will be found that the full cycle of Ufe may be indicated 

 in the foUo^dng circular form : — 



^ so that, starting with a spore 



I -,.,,^^ of one generation, and 



j/^"^ X ^\ travelling to our right hand, 



we return to another spore 

 which will give rise to a new 

 circle of life. 



(1) The spore is a simple 

 cell ; how produced we shall 

 hereafter see. It is, I say, 

 a simple cell, and not like the 

 seed of a phanerogam, a highly complex organism. The 



Fig. 4. — Spore 

 of Funariu 

 hygrometrica. 



After Schimper. 



spores are often seen to be emitted in vast 

 numbers from the cases in which they are 

 produced, and sometimes are brightly 

 coloured — red, green, or yellow. Fig. 4 

 represents (highly magnified) the spore of 

 a common Moss, the Fuuaria hygrome- 

 trica. 



(2) From the spore proceeds the proto- 

 nema, a line of cells, extending by transverse divisions, so that 

 it comes to consist of single cells joined end to end to one 

 another— an organism indistinguishable from the hypha of 

 an Alga. At points this hypha throws off lateral branches, 

 which are always of less diameter than the principal ones. 

 There is thus produced a tangled mat of fibres, running on 

 or near the surface of the ground, and often coloured by 

 chlorophyll. This is the green stufl:' so often seen in 

 flower-pots which have been allowed to get too damp. 

 At points in the primary hypha cells begin to divide in a 

 new fashion — not by transverse septa as 

 before, but by septa differently inclined, so 

 as to produce the rudiments of leaves ; and 

 the direction of growth changes from hori- 

 zontal to vertical. Thus is formed (3) the 

 bud, which by growth gives rise to (4) the 

 Moss plant. 



This course of development is illustrated 

 by Figs. 5 and 6. Fig. 5 shows at a 

 the remains of the cell which has burst 

 in emitting the hypha, or cellular projection to the 

 right. Fig. 6 shows the same plant further advanced in 



Fig. 5 — Spore 

 with young 

 Protonema. 



After Schimper. 



Fig. 2. — Polytrichum : an Acrocar- 

 pous Moss Female Plant, after 

 Dillenius. ar. Positiou of arche- 

 gone. s. Seta. a. Capsule and 

 appendages, o and c'. Capsule. 

 o. Operculum, cal. Calypfera. 



bridged 



Sporogone 



Moss Plant. 



Protonenia. 



Bud. 



Fig. 6. — Protonema with, a a, young Moss Plants forming on it ; r, 

 Ehizoids or Kootlets. After Schimper. 



life ; the hypha has been divided into numerous cells by 

 the transverse septa or walls ; lateral branches have grown. 

 Two letters a will be observed on the diagram. .\t the 

 left hand a the divisions of the cells have assumed a new 

 inclination so as to cut the cells into rudimentary leaves, 

 and we have the first promise of the Moss plant. At the 

 right hand a we have another Moss plant in a far more 

 advanced stage, showing distinct traces of leaves, and having 

 thrown out rootlets (c) downwards. The Moss plant when 

 mature assumes generally, but not universally, a form refer- 

 able to one or other of the two types already described, either 

 the pleurocarpous form shown by Fig. 1 or the acrocarpous 

 foi-m shown in Fig. 2. This Moss plant is a structure of very 

 considerable complexity, and often of great beauty of form. 

 Sometimes it assumes' the hkeness of some of the smaller 

 and more deUcate ferns ; but very rarely would it be 

 taken for a flowering plant, even by a casual observer. 



The Moss plant produces organs with two distinct 

 functions, comparable the one to the pistil and ovary, 



