appearance or characters, and probably represents the typical 
H. Sendineri, uninfluenced by crosses with 77. lycopodioïdes, which 
does not occur in the vicinity. On the sandhills, where it mingles 
with 4. lycopodioides and 4. Wilsoni, the forms of H. Sendineri 
are exceedingly abundant and very variable, Some cf them are so 
exactly intermediate as to be hardly assignable to either, and 
there are small forms showing some approach to 4. aduncum 
(typicum). I regard some of these dubious forms as hybrids, and 
do not consider they invalidate the claim of #. Sendtneri to be 
regarded as a distinct species. 
H. Wizsoni Schp. — This plant has been subordinated at one 
time: or another to A. Sendtneri, H. lycopodioides and 1. adun- 
cum. It approaches 7. lycopodioides in its robust habit, golden 
colour and porose basal cells, but in all other features is much 
more like /. Sendtneri. The typical plant seems to be interme- 
diate between these two species, and I am strongly inclined to 
regard it as a natural hybrid between them. In most of the loca- 
ities for A. Wilsoni the two supposed parents occur. The few 
localities in which I have hound 77. lycopodioides, or H. Stendtneri 
alone do not yield any forms resembling 4. Wilsoni. There dæs 
not seem to be any reason why two dioicous species s0 nearly 
related should not hybridise. Evidence from actual experiment of 
cross breeding in mosses is however very meagre, and we can 
only surmise what the probable results are likely to be. M 
Nicholson and others have described the influence of cross ferti- 
lisation on the sporophyte, but the further step of attempting to 
grow the hybrid spores does not seem Lo have been attempted. In 
many cases they would probably prove to be stérile. Amongst 
plants so closely related as those of « Harpidia adunca », regarded 
by som as all belonging to one arch-species, the probability is 
that they would be fertile. À few ripened capsules would yield 
enough spores to start the hybrid, which would then rapidly 
REVUE BRYOLOGIQUE ot  . 
increase and soon establish itself by the asexual methods of pro- 
pagation so freely indulged in by the Harpidia. Whilst Iregard 
H. Wilsoni in its typical form as a direct cross between 4, lyco- 
_podioides and H. Sendineri, here are several curious and aber- 
rant forms which recede still nearer Lo 4. Sendtneri. These pro- 
bably représent the hybrids Æ. Sendineri Wilsoni, and #4, adun- ca 
cum Wilsoni. On the whole Æ. Sendineri may be regarded as 
exhibiting little variability except where it is associated with 
H. lycopodioides ; and A. Wilsoni as a somewhat variable cross 
between the two. In the North of England I have found the pro- 
bable accuracy of this supposition lo some extent confirmed by 
