MICROSCOPIC EXAMINATION OF OVULE. 401 



sections (which, however, will seldom follow one tube continu- 

 ously 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 applying the pollen to the stigma 

 of several flowers, and then examining one or more of the styles 

 daily. " If the style of the 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 (heartsease) and Riles nigrum and 

 rubrum (black and red currant) are also good plants for the pur- 

 pose ; 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 EupJirasia ; 

 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 maybe discerned; and for this purpose, JEnothera 

 (evening primrose) has been had recourse to by Hoflmeister, 

 whilst Schacht recommends Lathrcea squamaria, Pedicularis pa- 

 lustris, and particularly Pedicularis sylvatica. There is no kind 

 of investigation that requires nicer management, and none which 

 is just now of greater interest to Botanists. Such Microscopists, 

 therefore, as have qualified themselves for the inquiry, by their 

 acquirement of the knowledge which is requisite to guide their 

 dissections, and of the manipulative skill by which alone these 

 dissections can be successfully made, cannot do a greater service 

 to science, than by applying themselves perseveringly to it. The 

 use of high magnifying powers is not at all needed. Much may 

 be done, in the preparation of the objects, under the Simple 

 microscope ; and for the examination of the preparations, a power 

 of 200 diameters with a shallow eye-piece is generally sufficient. 

 The assistance of the Binocular Microscope would probably be 

 found peculiarly valuable in this inquiry ; since the right inter- 

 pretation of the appearances presented, mainly depends upon a 

 precise knowledge of the exact relative position of the pollen- 

 tube, embryo sac, &c., such as this instrument is peculiarly fitted 

 to convey. 



258. 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 curi- 

 ous, and some are very beautiful, objects, when looked at in their 

 natural state, under a low magnifying power. Thus the seed of 



26 



