THE FALL OF THE COROLLA IN VERBASCUM. 317 
Besides the above meagre information, I may mention that 
M. Maury* attributes the falling of the corollas to traumatic 
action, and considers it one of the means (only secondary, in my 
opinion) for assisting fertilization. 
Observations on this subject, therefore, are by no means 
numerous; and Darwin’s statement is the only one which 
illustrates the phenomenon. For this reason I have thought 
that it would be of interest to publish the observations which 
I have made during the last two summers in order to satisfy 
myself as to the cause of the fall of the corollas in these plants. 
The phenomenon, without doubt, is to be ascribed to irri- 
tability, which is transmitted by the vascular bundles in an 
ascending line till it reaches the flower. In fact, if we gently 
strike one of the branches in the middle part, only the flowers 
will fall which grow above the place which has received the blow. 
Sir J. E. Smith and Darwin noted that the perfectly open 
corollas fall a few minutes after the shock given to the plant ; 
and if this really happens, we must add that (at least in Ver- 
bascum Lychnitis, Blattaria, floccosum, sinuatum, garganicum, 
phlomotdes, crassifolium, and in several of their forms and 
varieties), if the experiment be made in the early morning—say 
between 5 a.m. and 8 a.m.—the corollas only just opened (that is 
to say, when the sun rises) remain on the plant apparently 
insensible; but if the experiment be repeated in the afternoon, 
or on the following morning, not one of those corollas will 
remain on the plant. It is therefore, I think, to be inferred 
that some time is necessary after the expansion of the flowers 
before the tissues of the corollas are in a favourable condition to 
permit the corollas falling off in this manner. 
I. Of the Tissues of the Corolla. 
We will first examine Verbascum Blattaria, a common plant 
which grows in open grassy places, selecting a fully expanded 
flower which has already been open for some hours; and to 
prevent the corolla detaching itself from its calyx, we imbed 
it in glycerine-soap ; we then cut a microscopical section 
of the part of the corolla which connects it to the thalamus. 
* Maury, “ Observations sur la Pollinisation et Fécondation des Verbauscum,’ 
Bull. Soc. Bot. France, 1885, p. 53 . 
