22 
Professor Bommer on Lepidocarpon. 
Professor Bommer’s second point is the fact that so many of 
the megasporangia are without any integument. I have suggested 
that these specimens may represent the young stage of the organ in 
an arrested condition, to which our author objects that the sug¬ 
gested arrest of development only affects the external envelope, 
the megaspore, which is the essential part, being fully formed. 
Since my paper was published I have observed a non-integumented 
sporangium in which the megaspore already contains a prothallus, 1 
a fact which no doubt adds force to Professor Bommer’s criticism. 
Still, I can see no other explanation of the facts than that, from some 
cause or other (possibly the absence of pollination), certain sporangia 
were arrested in their development before the integument was formed. 
That among equally mature organs some should be with and others 
without such an important appendage, seems highly improbable, 
though perhaps a remote analogy might be found in the inconstancy 
of development of the indusium in some Ferns. 
Although I am not able wholly to accept Professor Bommer’s 
interpretation of the structure of Lepidocarpon, we are in substantial 
agreement in our views of the general significance of the type of 
fructification which it exhibits, and in our estimate of its biological 
importance. In his concluding paragraph Professor Bommer sums 
up the question in some admirable remarks with which I am 
entirely in accord. 
“ En resume, Lepidocarpon nous offre l’exemple d’ un 
Lycopodinee tres evoluee par l’accentuation d’une serie de dis¬ 
positions speciales, realisees deja isolement ou a un moindre degre 
chez d’autres Pteridophytes, Les characteres particuliers d’adapta- 
tion de son appareil de reproduction offrent, fonctionnellement, un 
parallelisme remarquable avec ce qui existe chez les Phanerogames.” 
D. H. SCOTT. 
’This section is in the Collection of Fossil Slides belonging to 
the Botanical Department of University College, Uondon. 
