London Horticultural Society and Garden. 617 



were incipient petals ; and the professor exhibited a tulip in which this 

 monstrosity might be distinctly traced. The pistil, stamens, and anthers, 

 Mr. Lindley said, he had described in a previous lecture, and he should now 

 only advert to them to prove that they are metamorphosed leaves. Im- 

 mediately within the petals of single flowers is found a whorl of stamens," 

 terminating in anthers laden with pollen. These stamens are nothing but 

 metamorphosed leaves, and in double flowers assume the shape of petals. 

 The pistil is in the centre of the flower, and consists generally of three 

 parts ; the style, the stigma, and the seed vessel ; the latter being composed 

 of one or more modified leaves, which are called carpella. The mid- 

 ribs of the folded leaves which have become carpella are sometimes 

 elongated into a style, their apexes forming the stigma. Other flowers, 

 the tulip for example, are without this member, and the stigma joins the 

 carpella. In all cases, however, it is the apexes of the leaves which form 

 the stigma, and this portion of the plant (as before observed) is the only 

 one uncovered by a membrane. 



The pollen consists of granules of cellular tissue, each containing a 

 mucous substance, composed of a number of molecules or minute bodies 

 always in motion. These are perceptible by means of a powerful micro- 

 scope, when a granule of pollen has burst, from having been some time 

 immersed in water. The granules of pollen, when fully ripe, fall on the 

 naked stigma, the moisture of which makes them swell, and burst, emitting 

 their mucus, which descends to the seeds contained in the carpella. 



Fruit is another stage in the modification of leaves. The lobes of an 

 orange are only carpella, thickened and enlarged, apparently by a pro- 

 vision of nature, to form a source of nourishment for the young plant 

 destined to proceed from the seed. This fleshy substance (including its 

 accompanying parts) is called the pericarpium, or shell of the fruit, which 

 exists in all plants, though in some it is so dry and thin as to be appa- 

 rently wanting. The formation of the lobes of an orange from the car- 

 pella of the pistil, Mr. Lindley illustrated by a preserved specimen of a 

 species of citron, called vulgarly fingers and thumbs, the points of which 

 did not adhere at the apex, but curved out like the stigma of some kinds 

 of plants. He also showed a pine-apple, every flower of which had pro- 

 duced a little pine, and a branch of larch which had thrown out a small 

 plant from its cone. As an example of the occasional thickening of other 

 parts of a flower, besides the carpella, Mr. Lindley showed a curious 

 specimen of a pear, or rather chain of pears, grown in Scotland, proceed- 

 ing one out of the other. 



Seed is always found in perfectly matured fruit, though its position is 

 various. It contains the embryo of the young plant, and is, in point of 

 fact, a detached bud. As soon as germination begins to take place, the 

 integument which envelopes the seed bursts, and the plumula (or stem) 

 and the radicle (or root) protrude themselves in opposite directions. The 

 solid part of the seed which is formed of one or more cotyledons, or thick 

 fleshy leaves, sometimes pushes through the ground (as in the case of the 

 annual lupine, &c), and forms the base of the stem. In this case, an 

 elongation of the collet or neck, which separates the cotyledons from the 

 radicle, takes place. In other cases, the cotyledons remain under ground, 

 and form a reservoir of nourishment for the young plant till the radicles 

 have acquired sufficient strength to absorb moisture for its support. The 

 cotyledons form another mark of distinction between the two great classes 

 into which nearly all plants are divided. Those with reticulated leaves, 

 and exogenous stems, having two cotyledons, and being called dicotyle- 

 dons ; while those with parallel-ribbed leaves and endogenous stems have 

 only one cotyledon, and are called monocotyledons. 



Lecture V. Cause of the Circulation of the Sap; Analogy between 



