E 
o» AND POLLEN IN SISYRINCHIUM, 119, 
separation of the outer coat, and as pointing out the nature 
of the longitudinal furrow of such common occurrence in 
almost all grains of pollen. 
With regard to the Ist point I must observe, that the for- 
“mation of granules by a process of division was first noticed 
‘by Mr. Brown, in Tradescantia virginica. The steps of the 
process differing chiefly in the late period, at which the 
nuclei lose their original containing cells, and in their form- 
ing ‘directly the grains of pollen, and not by the production of 
secondary nucleus. If I mistake not, but I quote from memo- 
ry, it was subsequently observed by M. Mirbel; an account 
of his observations being contained in the supplement to his 
observations on Marchantia. It was likewise nearly disco- 
vered by M. Brongniart, at a period earlier than either 
of the above, and had this excellent botanist observed the 
pollen in younger states in those cases to which he alludes 
of the cellules containing'an uncertain number of grains, 
it would no doubt not have escaped him. . The formation by 
division is precisely similar to the formation of the AERE 
of Mosses and Jungermanniz. 
The deciduousness or easy separation of the outer coat of 
pollen grains was likewise-first pointed out by Mr. Brown in 
Coniferz, and subsequently in Asclepiadez, in which latter 
instance, Mr. Brown did me the honour of demonstrating it. 
In the instance examined, it is perhaps nearly at its maximum. 
Nothing whatever is known of the nature of the furrow 
which I have mentioned as existing in the usual form of 
pollen. I consider it satisfactorily proved by this instance, 
which differs perhaps from all others, the inflected edges 
not becoming coherent. I consider it as a provision to allow 
of a certain degree of extension of the outer membrane, - 
without endangering the rupture of this, particularly as in 
some pollen, it may be obseryed to dilate gradually, and in 
all it disappears at length on immersion in water. And it 
is owing to this, that it is difficult to say whether it favours 
the exit of the boyaux or not.* 
e development of the pollen in another species of Zridez namely Par- 
danthus chinensis, see Journal of the Asiatic Society of Bengal, 1836, p. 732. 
