70 RHODOSPERME.E. 



principal varieties of conceptacular fruit, properly speaking. 

 But there are other bodies, called nemathecia, sometimes 

 confounded with fructification, but in which nothing resem- 

 bling spores are found. They exist as external warts, of 

 very irregular shape, often of considerable size and thickness, 

 composed altogether of vertical filaments, resembling those 

 of which the frond is composed (for they are only met with 

 in Crytonemiacea], but generally of larger calibre. I am 

 disposed to regard them as imperfect conceptacles, a view 

 which is favoured by their sometimes occurring (as in Phyl- 

 lophora membranifolia) on the same individuals that bear 

 proper conceptacles. With these nemathecia must not be 

 confounded the wartlike fructification of Gymnogonyrus, 

 which is a form of sorus, composed of tetraspores. 



The conceptacular fruit is perfectly regular in its position 

 and uniform in structure in the same species at all times. 

 It therefore bears every impress of being a normal function 

 of the Rhodosperrns, whether we consider its contents as 

 gemmules or spores. In the filiform kinds, as Polysiphonia, 

 the ceramidium is formed by the metamorphosis of one of 

 the ramuli ; but in the leafy genera of the same group 

 (Odonthalia, and many exotic genera) these organs spring 

 from the margin on the surface of the phyllodia, and can by 

 no means be regarded as altered ramuli, for they do not oc- 

 cupy the same position. Coccidia are very frequently seated 

 on the midribs in leafy plants, but occasionally occupy the 

 lamina ; and in ribless fronds they very frequently are 

 formed along the margin. Sometimes, in these last, they oc- 

 cur where the frond has been accidentally injured, and this 

 fact has been seized on to prove their abnormal character. 

 But the cases in which they are formed on definite points of 

 uninjured fronds greatly out-number those in which they 

 have been observed to spring from injured ones ; and the 

 latter must therefore be regarded as exceptions to a general 

 practice. On the whole, I am of opinion that the evidence 

 in favour of the conceptacles being a form of fructification 

 and not of gemmation, is at least as strong as that advanced 

 in favour of tetraspores, nor do I think that we are yet suffi- 

 ciently informed on the development of either fructification 

 to determine absolutely the relative value of tetraspore and 

 spore : that is, to which the term gemmule should be applied. 



In the mean time, certain arguments, supported by strong 

 analogies, appear to me to favour the supposition that the 

 contents of the conceptacles should be regarded as true 

 spores, or fructification ; and that the tetraspore is a gem- 



