MICROSCOPIC EXAMINATION OF OVULE. SEEDS. 431 



cally 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 favourable sub- 

 jects 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. u If the style 

 of flower of an Epipaclis (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 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 

 Orchicleous plants and in Euphrasia ; it being only necessary to 

 tear-open with a needle the Ovary of a flower which is just wither- 

 ing, and to detach from the Placenta the Ovules, almost every one 

 of which will be found to have a Pollen-tube sticking in its Micro- 

 pyle. These Ovules, however, are too small to allow of sections 

 being made, whereby the origin of the embryo may be discerned ; 

 and for this purpose, JEnothera (Evening Primrose) has been had 

 recourse to by Hoffmeister, whilst Schacht recommends Lathrcea 

 squamaria, Pedicularis palustris, and particularly Pedicularis 

 sylvatica. 



323. "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 magnifying power. Thus the Seed of 

 the Poppy (Fig. 231, a) presents a regular reticulation upon its 

 surface, pits for the most part hexagonal being left between pro- 

 jecting walls ; that of Caryophyllum (d) is regularly covered with 

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

 black hemispherical knob in its middle ; that of Amaranthus 

 hypochondriac us 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). 



