70 H. MARSHALL WARD. 



them. The meshwork of this rudimentary capillitium reminds the 

 observer of the ceratose skeleton of some sponges, a similarity which 

 is perhaps not lessened on examining the texture and composition of 

 the fibres. 



In concluding these remarks on the sporangium, a few words may 

 be added as to the action of reagents on the structures described. 

 Even in extreme cases it is possible, after removing all the calcium 

 carbonate by means of dilute acetic acid, to separate more or less 

 completely the outer network or membrane from the thin pigmented 

 proper wall of the sporangium (fig. 5) : the latter retains its even 

 colour and tough elastic character, but the external layer, if much 

 hardened by calcium carbonate, may be cracked in all directions under 

 the pressure of the cover slip. 



Solutions of iodine alone colour both the decalcified outer membrane 

 and the horny internal one yellow or brown, and the addition of 

 sulphuric acid enabled me to detect the blue colouration indicative of 

 cellulose in some parts at least of the inner membrane. This reaction 

 is by no means satisfactory however, and the rule is that when it 

 does make its appearance the blue colour is only in patches here and 

 there. The same is true of the reaction with carefully prepared 

 chlor. zinc iodine (Schulze's solution) : very often the only indication 

 of cellulose is a pale bluish-green patch here and there in the 

 membrane. Sulphuric acid causes partial solution of the test and 

 swelling of the fibres of the capillitium ; and the latter are coloured 

 bright golden brown by iodine, the colour only being rendered deeper 

 on the addition of sulphuric acid. 



Certain variability in these reactions of the walls and capillitium is 

 no doubt due, in part at least, to the age of the sporangium, as is the 

 depth of colour of the natural pigment : of course the depth of colour 

 is affected by the thickness of the membrane also, but this could 

 scarcely be a serious difficulty. In all the cases referred to the 

 spores, the only remaining contents of the sporangium, were ripe ; and 

 I now proceed to describe them. 



The ripe spore (figs. 5, 6, 7, and 10) in sporangia which have 

 become normally mature on roots in the solution, is a spherical cell, 

 T - Voin. in diameter, with a tough homogeneous cell wall, which is 

 coloured purple-brown, and appears to resemble the proper membrane 

 of the sporangium in all essential respects. With the usual reagents 

 the spore membrane yields better cellulose reactions, however, though 



