290 NOTES ON MASCAHENK OKCIlIUnLOGT. 



may possibly be the lierm aphrodite state of E. aeripta, t]iouq;h unfor- 

 tunately I cannot decide the point, my only knowledge of E. concolor 

 lieinp: derived from the above-quoted fijiure of Thouars. We have here 

 a probable analogne of the assumption of brilliant plumage by birds, 

 but with this difference, that with birds the couple in piesence of 

 which the moditieatiuns of colour have been induced is made up of 

 the separated sexual elements, while in the plant we have hermaphro- 

 ditism and unisexuaiity. As the blotching on the llower is assumed in 

 order to render it attractive to insects, this instance should rather be 

 compared witli the rare case where the female has become adorned ia 

 order to render her attractive to the male. 



Fcrtiliaation hi the bud. — This arrangement, shown by Darwin to 

 occur in Cephalanthera, and by Fitzgerald in two species of Thehj- 

 mitra, appears to exist in three genera belonging to the ilascarene 

 legion. In Puhjutachya zeylanicat Ldl. (P. hdeola, auct. div.), some of 

 the flowers liave, uj) to the time of expansion, slender ovaries which 

 cannot be distinguished from their pedicels ; in others the ovary is 

 swollen while the flower is still very small, and some time before it 

 has opened. The same thing was observed by Ayres in Phajtis 

 villosus, Kchb. f., who called the plant Calanthe inaperta, affording 

 by this sufficient proof of external difference between closed and open 

 flowers. The third case 1 have not seen ; the subject of it is the plant 

 figured by Thouars (I.e., t. 50) as Angraicum inapertum. In Cephalan- 

 thera Mr. Darwin found that but few seeds are produced when the 

 flowers are self-fertilised ; the contrary appears to be the case with 

 the Foli/stacliya, which, combining with it the scarcely distinguishable 

 and equally bud-fertilised P. luteola, Hook., has one of the widest 

 distributions known among Orchids. 



On methods for ensuring cross-fertilisation. 



(a.) In Avgrceeum and its allies. — The genera referred to here are 

 Angracum, Aeranthus, and Jjidrostachys, which, following Keichen- 

 bach, 1 have distinguished according to the structure of the poUen- 

 iipparatus. In Avgrceeum the caudiclc is single ; in the other two it 

 is double, Listrostaeltys having one gland, while Aeranthus has two. It 

 will be seen that this is a purely artificial arrangement, the structural 

 differences having little functional import, except perhaps in the case 

 of Aeranthus, where one can imagine a certain advantage to be derived 

 from the singleness of the pollen-attachment, each poUinium having 

 the chance of going twice or nearly twice as far as when both of them 

 are attached to one gland, provided that there be a sufiicient number 

 of fertilising insects. The varying structure of the labellum and ros- 

 tellum in these genera is, however, worthy of notice, and will be dealt 

 Avith in a few words. Each of these organs has three forms — the 

 labellum being either flat, concave, or convolute round the column, 

 while the rostellum consists either of two broad foliaceous lobes (fig 2), 

 or the thick lobes are united, so as to form a strong cone (fig. 3), or 

 else it is etiap-like, and projects over the entrance to the spur (fig. 4). 

 The flat or the concave labellum is usuaby associated with the 

 foliaceous rostellum, the latter partially filling up the entrance to 

 tlie spur, in which aim it is aided in Aeranthus sexquij/edaiis and in 



