“Part 111] THE MECHANISMS OF FLOWERS. 145 
and stigmas ripen together, and self-fertilisation takes place 
regularly; he says that in these forms no nectaries are present, 
‘since the aid of insects is not required. Unfortunately he does 
‘not name the species to which he refers, 
_ Anoda hastata, Cav.—Hildébrand figures and describes the 
proterandrous flowers. In the first stage the ripe anthers are 
erect and the stigmas are folded down, while in the second the 
stigmas project above the anthers (351). 
Gossypium herbaceum, L., has floral and extra-floral nectaries. 
‘It is visited by Ruby-throated Humming-birds, and by numerous 
‘insects (730). 
i Abutilon, Girtn—My brother Fritz Miiller has performed 
many experiments on this plant at Itajahy, with the following 
“results :— 
(1) All the species of Abutilon growing there, and their 
hybrids are barren (with perhaps one exception) when fertilised 
with their own pollen. 
(2) In those species which are unproductive with their own 
pollen, the pollen of their near relations (the parent-plants or 
their offspring) is less efficient than pollen from more distantly 
related or unconnected plants. 
(3) The application of pollen from several different species 
ives a greater yield of seed than pollen from a single other 
species Buty, 
(4) The simultaneous application of pollen of two species 
ways produces seedlings of two kinds: not as in the experi- 
ents of Koelreuter and Giirtner on other plants, where the 
i 
ic 
a 
a 
Simultaneous application of two species of pollen always produced 
8 seedlings of one kind only. 
(5) Among hybrids of the genus <Abutilon, there is more or 
less complete sterility between nearly related. individuals—between 
parent- -plants and their offspring, between offspring of the same. 
parents, or even between plants which have only one parent in 
common. 
By considering from a common point of view the diminution 
fertility in too close interbreeding and in the production of 
hybrids, Fritz Miiller arrives at the following law :—Every plant, 
| j0 produce vigorous and prolific offspring, requires a certain degree 
of difference between the male and female principles hil 
“coalesce ; and when this amount of difference is too great or 
too small, i.c. when the parent-plants are too distantly or too 
- closely related; the productiveness falls off. Further, the greater 
e. 
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