674 THE POPULAR SCIENCE MONTHLY. 



into one, with two midribs still remaining as evidence of their original 

 distinctness. 



Next, in the case of the petals, which alternate with the sepals of 

 the calyx, the relation to the stem is exactly reversed ; for we have 

 here two petals free and exterior, with one interior petal crowded 

 closely against the axis, thus : 



O 



a 



a a 



Here, then, the two external petals will be saved, exactly as the one 

 external sepal was saved in the case of the calyx ; and these two petals 

 are represented by the very small white lodicules nnder the outer pale 

 in our existing wheats and grasses. On the other hand, the inner 

 petal, jammed in between the grain and the inner pale (with the stem 

 at its back), has been utterly crushed out of existence, partly because 

 of its very small size, partly because of its functional uselessness, and 

 partly because it had no other part with which to coalesce, and so to 

 save itself as the inner sepals had managed to do. Moreover, it must 

 be remembered that the sepals do still perform a useful service in pro- 

 tecting the young flower before it opens, and in keeping out noxious 

 insects during the kerning or swelling of the grain ; whereas the lodi- 

 cules or rudimentary petals are now apparently quite functionless ; and 

 so we may congratulate ourselves that they are there at all, to preserve 

 for us the true ground-plan of the floral architecture in grasses. In- 

 deed, they have not survived by any means in all grasses ; among the 

 smaller and more degraded kinds they are often wholly wanting, hav- 

 ing been quite crushed out between the calyx and the grain. It is 

 only the larger and more primitive types that still exhibit them in any 

 great perfection. On the other hand, one group of very large exotic 

 grasses, the bamboos, has three regular petals, thus clearly showing 

 the descent of the family as a whole from rush-like ancestors, and also 

 obviously suggesting that the obsolescence of the inner petal in the 

 other grasses is due to their small size and their closely packed minute 

 flowers. 



Among the stamens, one-sidedness has not notably established 

 itself, for in wind-fertilized plants they must necessarily hang out 

 freely to the breeze, and therefore they do not get much crowded be- 

 tween the other parts. A few grasses still even retain their double 

 row of stamens, having six to each floret ; but most of them have only 

 one whorl of three. In some of the lower and more degraded forms, 

 however, even the stamens have lost their trinary order, and only two 

 now survive. This is the case in our own very degenerate little sweet- 

 vernal-grass, the plant which imparts its delicious fragrance to new- 

 mown hay. But in the cereals and in most other large species the three 

 stamens still remain in undiminished effectiveness to the present day. 



