148 
CONTRIBUTIONS TO BOTANY. 
and attributes its existence to the same origin. Subsequently, 
Mr. Wilson * traced the development of the ovule from its earliest 
stage to the final growth of the seed : but his account is not free 
from error ; for while he admits the great difficulty of discerning 
the exact limits of the secundine and embiyo-sac, he seems to 
have mistaken the elongation of the one for that of the other, as 
other observers had done before him. The drawings of Schleiden 
are certainly more correct than those of the latter botanist, as 
far as my observations extend. In examining the seeds of four 
Chilean species of Tropceolum, I found that this process is not 
the embryo-sac, which appears to have been absorbed : it may 
be seen that the extremity of the radicle is covered by a short 
tubular cap, which is continuous with the inner seminal integu- 
ment j this cap is formed by the doubling of the tubillus or 
lengthened neck of the tegmen ; and where this tubillus passes 
through the foramen of the outer integument, the latter closes 
round it by means of a glandular deposit f, well represented in 
Schleiden’s figures 124, 125, by the letter a, and in WUson’s 
figure 10 by the letter k. This reduplication of the neck of the 
tubillus is caused by the final growth of the tooth-like wings of 
the cotyledons, which, extending themselves upwards, conceal the 
radicle; and we have proof that the process here alluded to is 
really a reduplication of the tubillus, from the fact that at this 
part it is of greater opacity, and that when it is immersed in water 
under the microscope, air-bubbles are clearly discernible between 
the doubled membrane of the tube. It is certainly not a con- 
tinuation of the apex of the radicle, as St. Hilaire imagined, and 
does not offer any degree of analogy to the suspensor of Cycas : 
the extremity of the radicle is defined by a distinct rounded 
polished point, its apparent suspensor forming a lax covering 
around its apex. The subjoined figure 1 shows the form of the 
Fig. 1. Fig. 2. 
inner integument, where its mouth becomes extended into a 
very long neck or tubillus, which at the point of its origin be- 
* Lond. Journ. Bot. ii. 628, tab. xx. & xxi. 
t This is analogous to the glandular closing of the base of the tubillus 
in Ephedra, which Richard calls a “ tuberculura stigmaticum.” 
