. REVUE BRYOLOGIQUE 37 



in question agree fully with those of 2\ tortuosiwi, the 

 areolation, nerve section, etc. in no way differing. In 

 addition to this, two or three stems were found to all 

 appearance similar, at first sight, to the rest of the tuft, 

 but withthefmely tapering leaf-points and excurrent nerve 

 of the common species. Whether these stems belonged to a 

 separate plant or formed partof the plant in question it was 

 impossible to say ; there was at any rate nothing to indicate 

 that the former was the case. The nerve appeared to be 

 slightly wider in the bulk of the obtuse leaves, than in 

 those of the true tortuosum type, but not markedly so if 

 a large number were examined. 



If the plant in question belong to T. tortuosum it must 

 be considered rather as an abnormal sport than as a 

 genuine variety ; in that case it is certainly remarkable 



that out of some hundred stems, bearing many thodsand 



leaves, only two or three should be normal, and every leaf 

 on the rest, so far as one could judge, of the abnormal 

 form. In such instances of teratology one expects to find 

 considerable variation among the affected organs; here 

 the aberration from the normal type is so extreme and at 

 the same time so constant, that, if the theory of an abnor- 

 mal growth were rejected, I do not think it is too much to 

 say that it would fully justify a generic distinction. 



Since writing the above I have received from Prof. 

 Barker another plant which not only is interesting in itself, 

 but goes some way to confirm the teratological explanation 

 of the plant already described. This is a small form of 

 Ceratodon purpiircus, in which the uppermost leaves on 

 most of the stems, and all the leaves of others, end in 

 preciselv the same wide, rounded , almost spathulate 

 manner" as those described above instead of gradually 

 tapering to an acute point as is usual in this species, and 

 as in fact is the case with many of the lower leaves, and, 

 on a stem or two here and there, with all of them. The 

 nerve in the abnormal leaves ceases at some distance 

 below the apex ; the margin is frequently recurved round 

 the whole of the broad, obtuse apex of the leaf. 



It is pretty clear from a comparison of the two plants, 

 that the same cause has produced this curious result in 

 both cases, but in the one plant it has affected all the leaves 

 alike, in the other, as is usual in such cases, it has acted 

 spasmodically, a single stem often showing a great variety 

 of forms, from the most obtuse and extreme form to the 

 normal type of Ceratodon pur pur cits. 



Wickham House, East Park Parade 23, Northampton (England), March 1, 1900. 



H. N. Dixon. 



