USE OF THE MICROSCOPE IN BOTANY. 31 



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 

 favourable 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. i If the 

 style of flower of an Epipactis (says Schacht), to which 

 the pollen has been applied about eight days pre- 

 viously, 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 (heart's-ease) 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 en- 

 trance of the pollen-tube into the micropyle* may 

 be most easily observed in orchidious plants and in 

 Euphrasia; 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 dis- 

 cerned ; and for this purpose, (Enothera (evening 

 primrose) has been had recourse to by Hortmeister, 

 whilst Schacht recommends Lathr&a squamaria, 

 Pedicularis palustris, and particularly fedicularis 



* From juxpoc, " small," and <7rw\n, "a gate," the minute perfora- 

 tion through the skin of a seed. 

 t Dr. Carpenter on the Microscope, p. 430. 



