THE BULBIFORM SEEDS OF CERTAIN AMARYLLIDE^E 377 



contained two anatropons ovules, the development of which Baillon 

 found to be at first 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. v.). 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 Pjianzenhlologische Scldldeningen (i. 

 p. 129) (1889),* has given a detailed account of the development 

 of the seed in Crinum miaticum. The ovules, of which there are 

 two in each of the three ovary-chambers, recall in their extremely 

 rudimentary structure 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 fertilization the embryo-sac becomes filled 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, where we find chlorophyll developed in the 

 cell-layers. Ultimately a thin protective coating of cork is formed. 

 Thus the ripe seed consists simply of a mass of endosperm enclosing 

 an embryo. The endosperm forms a soft fleshy mass, in which are 

 air-containing intercellular spaces, forming, as Goebel suggests, an 

 adaptation for the distribution of the seeds by water, their specific 

 gravity being thereby considerably reduced. The peripheral cork- 

 layer prevents water- logging. A similar device occurs in some 

 Water Lilies, where an additional seed-coat (the aril) forms a 

 light air-containing float. 



To sum up the results of previous work on the bulbiform seeds 

 of Amaryllidea, we find that three forms can be distinguished, as 

 follows : — 



A. True seeds. 1. Developed from a normal ovule, the outer 

 integument of which becomes thick and fleshy after fertilization, 

 and forms the substance of the bulbiform mass, e.g. HymenocalUs. 



2. Developed from a naked ovule, the fleshy substance being 

 derived entirely from the endosperm, which develops chlorophyll in 

 its outer layers and continues to grow for some time, e. g. Crinum 

 asiaticum, and other species. 



B. A vegetative growth replacing the seed. 



3. A normal ovule is produced, but a viviparous growth of an 

 adventitious shoot and root takes place at its base, and a bulbil 

 is formed, the ovule integuments forming the outer coats, e.g. 

 Calostemma Cunninghami. 



