botanical Collections. 185 



«f the liilum and chalaza. 2, The great force of development of one of 

 the sides of the ovule. 3. The inertness, or even contraction, of the 

 opposite side. This last remains stationary, or is subject to diminution, 

 while the other elongates. If the side that elongates had been free in its 

 development, it would have proceeded in a straight line ; but it is influenced 

 by the inertness or contraction of the opposite one, and can only increase by 

 turning round the other, as a centre of resistance. Hence the annular form 

 assumed by most of the campulitropous seeds. 



By only considering seeds in a general way, we should now be tempted to 

 infer, that all might be arranged in one or other of the three classes above 

 mentioned ; but, on a more narrow inspection, we shall find, that the 

 characters of one sometimes combine with those of another ; that, in certain 

 species, similar results arise from different causes ; that examples occur, in 

 which the developments are arrested before they attain the perfection of the 

 type to which they seem to belong ; or even that, by too great a development, 

 they may give rise to anomalous forms. In this point of view, the field of 

 observation becomes extensive, since seeds ai'e different in different natural 

 orders. M. Mirbel has already remarked many curious modifications, one 

 or two of which we shall here notice : — 



According to the common law in Quercus, Cori/his, Alrais, &c. the incipient 

 ovule is orthotropous : it enlarges without having its position altered. 

 Now, all the upper portion receives very little increase to its size, but the 

 lower becomes much larger, elongating at the base, and carrying off with it 

 the chalaza, which thus removes from the stationary hilum to within a short 

 distance from the vortex of the ovule : separation of the chalaza from the 

 hilum cannot have taken place without forming a lateral raphe, so that here 

 we have all the characters of the anatropous seed, although the ovule has 

 preserved its original position. 



The presence of a raphe may also be observed in the campulitropous type, 

 and this anomaly happens when the first development of the ovule is simi- 

 lar to that in the anatropous ovules. In the pea, the young ovuluni becomes 

 entirely inverted; the summit takes its station at the hilum, and the base, 

 where the summit was ; and from the hilum to the chalaza, which is diame- 

 trically opposite to the exostome, the raphe is to be observed. If the 

 developments were at an end, the seed would thus be anatropous : but it 

 is only the side, on which the raphe is, that remains stationary; the other 

 continues to increase, and the campulitropous form soon prevails over the 

 anatropous. The seed of the pea then exhibits the combination of two 

 types ; it is termed amphitropous. 



We shall cite one more example, and a very remarkable one. In general, 

 it is a rule that the radicle points to the exostome, while the other extremity 

 of the embryo is at the chalaza ; but this position is different in the campu- 

 litropous ovule of the Primulacece and Plantaginea ; and the anomaly results 

 from the inequality of the developments. The primine, in consequence of 

 an extraordinary increase of the extensible side, and gradual contraction of 

 the opposite one, has quickly the exostome turned towards the chalaza, and 

 these two extremities are not long in coalescing ; but the extensible side of 

 the secundine, as well as that of the tercine, ceasing to increase with the 

 corresponding side of the primine, it follows that the embryo, the radicle 

 of which ncA'-er separates from the summit of the internal envelopes, remains 

 Stationary with the endostome, \vhile the exostome pursues its course, and 

 does not stop till it reaches the base of the ovide. 



M. Mirbel concludes, from his numerous observations, that the develop- 

 ment of the ovule is generally the same in all the species of one natural 

 family ; and thus, he considers, that researches of this kind must be not only 

 useful to the progress of vegetable anatomy and physiology, but to philoso- 

 phical botany, inasmuch as they furnish characters, the more important, as 

 they give to classification the sanction of physiology. 

 VOL. III. 2 A 



