270 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VOL. V. 



relative positions of the two liquids by the clock movement, and the 

 accompanying agitation, were found to overcome these inconveniences. 

 Unfortunately, this device was hit upon only after numerous experi- 

 ments, and when the investigation was almost completed. The trans- 

 ference from benzole to parafifine was effected in a stationary dialyzer, 

 or by evaporating off the benzole in a water-bath, from a ten per cent, 

 solution of paraffine in benzole. Celloidin embedding has also great 

 advantages, but as the material has to be cut into slices not thicker than 

 two millimetres at most, and as the prothallia were often nearly twenty 

 millimeters in length, it was only employed for sections through certain 

 regions of the gametophyte, and for the much less impenetrable young 

 sporophyte. The stains chiefly used were either a combination of 

 alum-cochineal and eosin, or aqueous safifranin, made by dropping a 

 small amount of saturated alcoholic solution of equal parts of Griibler's 

 alcohol and water soluble saffranins. This last method seems worthy 

 of a wider application. 



IV. 



The youngest prothallia obtained were already two millimetres in 

 length by one and a-half in breadth. As may be seen from figure i, 

 they are of flattened oval shape, and covered with hairs. The growing 

 point is at the narrow thin end, and the prothallium thickens and 

 widens from thence backwards. Antheridia alone are found at this 

 stage, and are entirely confined to the upper surface of the gametophyte. 

 They form a cluster at the older end, but thin out into a narrow median 

 row as they extend forward towards the growing point, figure i, ar. 

 In somewhat larger and older plants, the iriedian row of antheridia is 

 raised on the crest of a distinct ridge, and the archegonia begin to make 

 their appearance upon its sides, figure 2. The antheridial ridge is a 

 marked feature of most of the older prothallia, and must have the same 

 significance in the process of fertilization as the inferior archegonial 

 prominence possesses in the leptosporangiate Filicineco. In more 

 mature individuals the ridge is obliterated, especially in the posterior 

 region of the prothallus, by the more rapid growth of the sides of the 

 latter, which seems to be a provision for the nourishment of the fertilized 

 archegonia. This phenomenon probably is the cause of the antheridial 

 ridge not being noticed by Campbell 9. Figure 3 shows a plant in 

 which an embryo, evi., has already reached a considerable size. The 

 antheridial prominence is still very marked ; the root-hairs, however, 

 have largely disappeared. In figure 5, we have a somewhat younger 

 stage with the rhizoids still abundantly present, especially in the 



q. Op. Cit. 



