THE COMMENCEMENT OF THE PHANEROGAMIC FRUIT. 81 



wering plants we find a definite central mass of cells, the nucellus, surrounded 



a well-marked sheath, the coat or integument. Generally the integument is 

 able, as in Delphinium and Butomus (cf. figs. 210 ^- "■ i"), in other cases it is 

 Lgle, as in Compositse, Umbelliferse, Hippuris and Gycas revoluta {cf. fig. 208^). 



most Orchids the nucellus is inclosed in a large-celled, inflated and transparent 

 tegument, through which it is distinctly visible {cf. fig. 212^). In not a few 

 iphytic Orchids, however, this contrast of parts is only imperfectly shown, whilst 



the Balanophorese and various other parasites no trace of the distinction into 

 cellus and integument is found. In all cases where an integument is present 



is discontinuous at one point, where the nucellus is uncovered. This is the 

 icropyle. Sometimes the micropyle is at the apex of the ovule, but in a very 

 rge number of cases the whole ovule is bent over so that the micropyle is situated 

 )se to the point of attachment of the ovule. The ovule may be attached to its 

 pport {placenta) by means of a filamentous cord, or it may be directly seated upon 

 The common condition of an inverted ovule fused with its filamentous stalk is 

 own in figs. 208* and 210^**. The filamentous stalk is technically known as 

 e funicle, and the ridge where it is fused with the ovule as the raphe {cf. vol i. 



644). 



The cells of the nucellus of the ovule show a very unequal growth. One of 

 em enlarges in a conspicuous manner, and is known as the Emhryo-sac. In 

 jnifers it attains relatively to the other cells of the nucellus enormous dimensions, 

 hilst in most other flowering plants as it grows it encroaches upon the other cells 



the nucellus till only a single layer remains surrounding it. And even this layer 

 ay be in part absorbed, so that the embryo-sac actually penetrates to the 

 icropyle. The protoplasmic contents of the embryo-sac is richly vacuolated, but 



the end directed towards the micropyle vacuoles are absent, and the protoplasm 

 eaks up into several distinct protoplasts, each of which is provided with a con- 

 icuous nucleus but in the first instance with no ceU-membrane. As a rule three 

 ch protoplasts are found at the micropylar end of the embryo-sac; of these one 

 ily gives rise, after fertilization, to an embryo. This cell is the ooplast or " ger- 

 inal vesicle ", the other two are named synergidce {of. also, figs. 316 and 316). 



In the ovaries of Orchids, as shown in figs. 212 1-^'*'*, the ovules arise in great 

 imbers upon peculiar furrowed ridges of the carpels. They arise from the super- 

 ial cells of these ridges, and are not provided with any vascular-bundle connec- 

 )ns; in fact, they are comparable to those epidermal structures known as hairs or 

 chomes. This analogy is emphasized by the fact that in the ovaries of many 

 •chids real hairs are present, as, for instance, in Lcelia Perrinii and Gcelogyne 

 xntaginea, transverse sections of which are represented in figs. 212 1- ^' ^' *. In 

 ese remarkable species six ridges project from the wall into the ovarian cavity, 

 d from all of these hair-like structures are developed. The three ridges belong- 

 r to the curious excavated receptacle, already described, alone bear ordinary 

 icellular hairs, the others bear ovules, one of which is shown in fig. 212 ^. 



The ovules of Cycads are very differently developed, as may be seen from a 



VOL. II. 56 



