180 Mr. A. Henfrey on some Points in the Structure 
a brief notice ; it is this : “ Spiders are reputed to be subject to 
the stone : I do not say Calculus in Vesica ; but we are informed 
by Lesser that Dr. John Franck having shut up fourteen spiders 
in a glass with some valerian root, one of them voided an ash- 
coloured calculus with small black dots.^^ This singular opinion 
seems to have originated in a misapprehension of an ordinary 
occurrence, which I shall proceed to explain. If the faeces of 
spiders, which consist of a white fluid comprising black particles 
of greater density, happen when voided to be suspended in the 
webs or among the lines spun by these animals, they assume, 
under the influence of molecular attraction, the spherical figure 
common to fluids in general when similarly circumstanced, and 
soon becoming indurated by desiccation, a change of colour from 
white to gray or grayish brown spotted with black uniformly 
takes place, and in this state they constitute, I doubt not, the 
substance which Dr. Franck mistook for a calculus. 
XVIII. — On some Points in the Structure and Growth of Mono- 
cotyledons. By Arthur Henfrey, F.L.S. &c.* 
[With two Plates.] 
Although the views which are advocated in the following paper 
do not possess much originality, I have been induced to lay my 
observations before this Section by several considerations. In the 
first place, I believe that the subject is one to which a compara- 
tively small amount of attention has been paid in this eountry, 
and therefore, dependent as we have been on foreign observers 
for our knowledge of it, indigenous investigations may have some 
interest; secondly, the theories of monocotyledonous structure 
held by the chief continental authorities are at present not ge- 
nerally-received views, but to some extent individual opinions, 
conflicting more or less one with another ; and, lastly, as I have 
devoted a considerable amount of time to the examination of this 
most intricate subject, I have thought that independent obser- 
vations, carefully and repeatedly made, might by their publica- 
tion be of some service to the science of Botany, either by point- 
ing out the errors or confirming the statements of other ana- 
tomists. 
I have directed my attention to the structure of those Mono- 
cotyledons which can be readily obtained in a living state in this 
country ; the structure of the stems of Palms I have not had the 
opportunity of studying, and therefore with regard to them I 
have been obliged to depend upon the observations of others. So 
* Read at tlie Meeting of the British Association, June 1847, and com- 
municated by the Autlior. 
