386 THE MICROSCOPE AND ITS REVELATIONS. 



instructions, however, may prove useful to such as would like to inform 

 themselves as to the mode in which the generative function is performed 

 in Phanerogams. In tracing the origin and early history of the ovule, 

 very thin sections should be made through the flower-bud,* both vertically 

 and transversely; but when the ovule is large and distinct enough to be 

 separately examined, it should be placed on the thumb-nail of the left 

 hand, and very thin sections made with a sharp razor; the ovule should 

 not be allowed to dry-up, and the section should be removed from the 

 blade of the razor by a wetted camel-hair pencil. The tracing-downwards 

 the pollen-tubes through the tissue of the style, may be accomplished by 

 sections (which, however, will seldom follow one tube continuously for 

 any great part of its length), or, in some instances, by careful dissection 

 with needles. Plants of the Orchis tribe are the most favorable subjects 

 for this kind of investigation; which is best carried-on by artificially apply- 

 ing the pollen to the stigma of several flowers, and then examining one or 

 more of the styles daily. "If the style of flower of an Epipactis (says 

 Schacht), to which the pollen has been applied about eight days previously, 

 be examined in the manner above mentioned, the observer will be surprised 

 at the extraordinary number of pollen-tubes, and he will easily be able to 

 trace them in large strings, even as far as the ovules. Viola tricolor (Hearts- 

 case) and Ribes nigrum and rubrum (Black and Red Currant) are also good 

 plants for the purpose; in the case of the former plant, withered flowers 

 may be taken, and branched pollen-tubes will not unfrequently be met 

 with." The entrance of the pollen-tube into the micropyle may be most 

 easily observed in Orchideous plants and in Euplirasia; it being only 

 necessary to tear-open with a needle the ovary of a flower which is just 

 withering, and to detach from the placenta the ovules, almost every one 

 of which will be found to have a pollen-tube sticking in its micropyle. 

 These ovules, however, are too small to allow of sections being made, 

 whereby the origin of the embryo may be discerned; and for this pur- 

 pose, CEnothera (Evening Primrose) has been had recourse to by Hofl> 

 meister, whilst Schacht recommends Lathrcea squamaria, Pedicularis 

 palustris, and particularly Pedicularis sylvatica. 



390. We have now, in the last place, to notice the chief points of 

 interest to the Microscopist which are furnished by mature seeds. Many 

 of the smaller kinds of these bodies are very curious, and some are very 

 beautiful objects, when looked-at in their natural state under a low mag- 

 nifying power. Thus the seed of the Poppy (Fig. 278, A) presents a 

 regular reticulation upon its surface, pits for the most part hexagonal 

 being left between projecting walls; that of Caryopliyllum (D) is regularly 

 covered with curiously-jagged divisions, every one of which has a small 

 bright black hemispherical knob in its middle, that of Amarantlms hypo- 

 chondriacus 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 that of many Bignoniacece is remarkable 

 for the beautiful radiated structure of the translucent membrane which 

 surrounds it (E). This structure is extremely well seen in the seed of 

 the Eccremocarpus scaber, a half-hardy climbing plant now common in 

 our gardens; and when its membranous ( wing' is examined under a suffi- 

 cient 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) are thickened so as to form radiating ribs for the support of the 

 wing, whilst the front and back walls (which constitute its membranous 



