724 MICROSCOPIC STRUCTURE OF PHANEROGAMIC PLANTS 



middle ; that of Amaranthus hypochondriacus has its surface traced 

 with extremely delicate markings (B) ; that of Antirrhinum is 

 strangely irregular in shape (C), and looks almost like a piece of 

 furnace-slag ; and those of many Bignoniacece are remarkable for the 

 beautiful radiated structure of the translucent membrane which 

 surrounds them (E). This structure is extremely well seen in 

 the seed of Eccremocarpus scaber, a half-hardy climbing plant 

 common in our gardens ; and when its membranous ' wing ' is 

 examined under a sufficient magnifying power, it is found to be 

 formed by an extraordinary elongation of the cells of the seed-coat 

 at the margin of the seed ; the side-walls of which cells (those, 

 namely, which lie in contact with one another) being thickened so as 

 to form radiating ribs for the support of the wing, whilst the front 

 and back walls (which constitute its membranous surface) retain their 

 original transparence, and are marked only with an indication of 

 spiral deposit in their interior. In the seed of Dictyoloma peruviana, 

 besides the principal ; wing ' prolonged from the edge of the seed- 

 coat, there is a series of successively smaller wings, whose margins 

 form concentric rings over either surface of the seed ; and all these 

 wings are formed of radiating fibres only, composed, as in the pre- 

 ceding case, of the thickened walls of adjacent cells, the intervening 

 membrane, originally formed by the front and back walls of these 

 cells, having disappeared, apparently in consequence of being un- 

 supported by any secondary deposit. Several other seeds, as those 

 of Sphenogyne speciosa and Lophospermum erubescent, possess wing- 

 like appendages : bnt the most remarkable development of these 

 organs is said by Mr. Quekett to exist in a seed of Calosanthes 

 indica, an East Indian plant, in which the wing extends more than 

 an inch on either side of the seed. Some seeds are distinguished by 

 a peculiarity of form which, although readily discernible by the 

 naked eye, becomes much more striking when they are viewed under 

 a very low magnifying power. This is the case, for example, with 

 the seeds of the carrot, whose long radiating processes make it bear, 

 under the microscope, no trifling resemblance to some kinds of star- 

 fish ; and with those of Cyanthus minor, which bear about the same 

 degree of resemblance to shaving-brushes. In addition to the pre- 

 ceding, the following may be mentioned as seeds easily to be 

 obtained and as worth mounting for opaque objects : Anagallis, 

 Anethum graveolens, Begonia, Carum carui, Coreopsis tinctoria, 

 Datura, Delphinium, Digitalis, Palatine, Erica, Gentiana, Gesnera, 

 Hyoscyamus, Hypericum, Lepidium, Limnocharis, Linaria, Lychnis, 

 Mesembryanthemum, Nicotiana, Origanum onites, Orobanche, Petunia, 

 Reseda, Saxifraga, Scrophidaria, Sedum, Sempervivum, Silene, 

 Stellaria, Symphytum asperrimum, and Verbena. The following 

 may be mounted as transparent objects in Canada balsam : 

 Drosera, Hydrangea, Monotropa, Orchis, Parnassia, Pyrola, Saxi- 

 fraga. 1 The seeds of umbelliferous plants generally are remarkable 

 for the peculiar vittce, or receptacles for essential oil, which are 

 found in the closely applied pericarp or seed-vessel which encloses 



1 A part of these lists have been derived from the Micrograpliic Dictionary. 



