Tubiflorce. 
297 
under consideration. Quite 60% of the total number of species 
included in this order belong to the very natural genus Solarium, 
the flowers of which are of the type characteristic of what we have 
named the “ Transitional Group ” ; they are regular, with isomerous 
androecium, and the bicarpellary ovary contains an indefinite 
number of ovules: this latter condition is virtually universal 
throughout the Solanaceae. The flowers of Solatium shew speciali¬ 
zation in the androecium, the anthers being connivent, often coherent 
and with an opening at the tip—much as in Borago . 
For the remaining genera, most of the forms concerned are of 
the same “ transitional ” type ; but a definite tendency to zygomorphy 
is observable in the greater or less development of the corolla-limb 
on one side (e.g., Petunia, Nicotiana), and also in the frequent 
inequality in length of the stamens even though these be isomerous 
with the corolla. 
Similar hints at zygomorphy, rare but significant, are to be 
found among the the orders already considered—e.g., Echium, 
Lycopsis, Macromeria, in Boraginaceae; Bonplandia in Polemoniaceae. 
Another primitive form which zygomorphy may take consists in the 
lateral placing of the stamens relatively to the perianth, in flowers 
where the stamens are exserted. The flowers in such cases usually 
face laterally, or are pendulous, and the exserted portions of the 
filaments tend to hang downwards, more or less; but the terminal 
parts, bearing the anthers, are upturned. A good example of this 
is Cobcea scandens (Polemoniaceae), a commonly cultivated green¬ 
house climber, but the phenomenon is by no means uncommon in 
flowers otherwise quite regular. Light doubtless has played a 
considerable part in the production of this condition, but the 
adaptation to the reception of insect-visitors is obvious. We shall 
have need to consider yet another type of Zygomorphy, the 
outcome of inequality in the calyx-lobes, when we deal with the 
Rubiaceae. 
Finally, in the tribe Salpiglossideae, the number of fertile stamens 
is rarely so great as the number of corolla-segments; the androecium, 
in fact, is oligomerous in nearly 90 species (e.g., Brunfelsia, 
Schwenkia, Anthocercis), and the stamens are arranged didynamously 
in the manner characteristic of the Lamiales and Personales. 
Intermediate stages, in which one or more stamens are represented 
by sterile staminodes, occur; while the extreme case, in which the 
androecium consists of two fertile stamens only, is found in, e.g., 
Schizanthus, a commonly cultivated plant with strongly zygpmorphic 
flowers. 
