* 
MR. W. GRIFFITH ON THE GENUS GNETUM. | 305 
e» 
same parts in ordinary ovula, precludes the necessity of any remark ; neither is there any 
feature in the embryo, excepting its enormously long funiculus, that would lead me to 
suspect any material deviation from the usual structure. ` Å 
The only genera of Comiferæ with which I have been able to compare Gnetum are 
Agathis and Thuja, in both of which the nucleus has only one envelope, its cavity being 
in Agathis lined with a very distinct amnios. The males of neither of these genera, how- 
ever, exist in the Botanical Garden at Caleutta; and neither of them appears to possess 
that power, which exists to such a degree in Oycas and Gnetum, of continuing the deve- 
lopment of the ovulum independently of fecundation. With Cycadeæ I have had ample 
opportunities of comparison, so far, at least, as regards the young ovula and perfect fruit. 
The mutual resemblance is, indeed, so strong, that I have little hesitation in affirming 
that the fruit of Cycas differs only materially from that of Gnetum in the absence of 
an additional envelope, and perhaps in the presence of the remains of the amnios. With 
regard to the ovula of Cycas, the nucleus has, as Dr. Brown has stated in the Memoir 
referred to, p. 24, only one envelope; but I have no doubt, both from the difference in 
its tissue, in which there is, indeed, an obvious line of demarcation, as well as from the 
disposition of its vessels, that it consists of two, united throughout their whole extent. 
The nucleus is likewise united by its lower portion to the envelope,—its apex, which is 
conical, being free, and prolonged into a membranous point, which is engaged within 
the lower part of the canal formed by the opening that exists through the coat. This 
membranous portion is tubular, the cavity extending some distance within the actual 
substance of the nucleus : its walls are cellular, and not lined by any membrane. 
The body of the nucleus contains a large globular cavity, in which a sac of a corre- 
sponding size and form exists. This sac (the amnios) is, at the period referred to, mem- 
branous, and is rendered tense by an abundant gelatinous fluid; it is easily detached, and 
appears to be merely applied to the walls of the cavity. 
I hope to be H Bone future period to enter into more detail on the subject of the 
development of the ovula of Cycas, which appears to promise several yr al and na 
interesting facts, particularly as regards the first appearance of cellular Hesne E; 
the sac of the amnios, while at the same time its great size renders it peculiarly fitted Ar 
observation. ge ER | Li 
It is probable that the fruit represented by Dr. Hooker (Bot. Mag. gi em 
t. 2827) as that of Cycas circinalis, belongs to another ne The true MEG of 
has, as Richard has stated, a fungous envelope surrounding the albumen, \ iini 
considerable thickness towards the base of the fruit, or rather seed ; a a ye ae 
probably the remains of the amnios, being interposed, and OaE 9 ES har 
velope, except towards its apex. In this species the cotyledons ifii i AER 
likewise stated, united, except at their bases, where å ipu deep z 
coats, agrees much 
ge intion, particularly as regards the coats, : 
on both sides. Dr. Hooker's description, particularly apex of the albumen, first pointed 
better with C. sphærica, Roxb. The sacs existing in the | 
| rman in whic! "yo is develo 
out by Dr. Brown *, are in C. circinalis permanent ; that in which the embryo ped 
* Prodr. Flore Nova Hollandie, vol. i. p. 347. A 
VOL. XXII. 
