THE BULBIFORM SEEDS OF CERTAIN AMAKli^LLIDE.E. 95 



quite normal ; two integuments enveloped the nucellus, in the centre of 

 which was apparently an embryo-sac. But instead of producing a seed, 

 the ovule developed directly into a bulbil in the following manner (fig. 24). 

 It became very much swollen at the base {chalaza), forming a disc-like 

 structure, from the centre of which a root grew outwards and a conical bud 

 inwards, occupying the central ovular cavity and growing up towards the 

 micropyle. At the same time the integuments became fleshy, and formed, 

 together with the remains of the nucellus, the outer scales of the bulbil. 

 Finally Goebel, in his " Pflanzenbiologische Schilderungen " (i. p. 129) 

 (1889), has given a detailed account of the development of the seed in 

 Criniim asiaticum. The ovules, of which there are two in each of the 

 three ovary-chambers, recall in their extremely rudimentary structure 



Fig. 24. — Calostcmma Cunninghami, Ait. 



1. Two anatropous ovules — m, micropyle; a, an aril-like outgrowth which 

 ultimately forms a cap on top of the bulb. 



2. Longitudinal section of one of the ovules shown in 1, showing the inner, 

 i, and outer, i', integuments surrounding the nucellus, n, in which is seen the 

 embryo-sac, s ; m, micropyle ; h, hilum, or point of insertion of the ovule. 



3. Longitudinal section of an ovule at a later stage — the base (chalaza) has 

 become flattened, forming a disc, from the lower part of which a root, r, is grow- 

 ing, from the upper a bud, 6, which is filling the cavity of the embryo-sac. 



4. Mature bubil in longitudinal section. The bud has completely filled the 

 cavity of the nucellus, the remains of which, together with the integuments of 

 the ovule, form the bulb-scales. 



(After Baillon, in Compt.-Rend. de la 2me Session, Assoc. Franc. [1874], t. iii.) 



those of parasitic plants. They are naked, consisting merely of an 

 elongated swelling on the placenta, in the centre of which is an embryo- 

 sac (sometimes two embryo-sacs occur in one ovule). After fertilisation 

 the embryo-sac becomes tilled with endosperm, in which the small embryo 

 is enclosed ; occasionally a central narrow space remains in the endosperm, 

 which Goebel suggests may be the central cavity referred to by Brown in 

 those seeds in which he found no embryo, the latter from its small size 

 having been overlooked. The endosperm continues to develop, growing 

 out of the nucellus (of which only a small portion remains at the base), 

 and forms a large fleshy mass, completely surrounding the small axial 

 embryo. This growth in thickness takes place chiefly on the outside. 



