MICROSCOPE IN THE GARDEN. 29 



(Fig. 121, PL 5). In the hazel and many of the 

 grasses they are triangular (Fig. 122, PI. 5) ; in 

 the heath they are trilobed (Fig. 123, PL 5) ; in 

 the dandelion, and many of the compositous order 

 of plants, they are beautifully sculptured (Fig. 

 124, PL 5). In the passion-flower three rings are 

 observed upon them, as though they had been 

 formed with a turner's lathe (Fig. 125, PL 5). In 

 the common mallow they are covered all over with 

 little sharp-pointed projections, like a hand-grenade 

 (Fig. 126, PL 5). The microscopic observer should 

 make himself acquainted with the forms of pollen 

 grains, as, on account of their small size and light- 

 ness, they are blown about in all directions, and 

 may be found on very different objects from those 

 in which they have been produced. Some absurd 

 mistakes have been committed by confounding pol- 

 len grains with other forms of organic matter. 



The pistil, which is the central- organ, seated in 

 the midst of the stamens in the flower of plants, 

 will afford a great variety of interesting points for 

 examination with the Microscope. In the earliest 

 stages of the growth of the pistil, thin sections of 

 it may be made, and the position of the ovules 

 observed. In the ovule will be found the embryo 

 sac, a central cell, which, on being brought in 

 contact with the pollen grain, grows into the seed. 

 The seed contains the embryo, or young plant. In 

 most plants this is sufficiently large to be* seen 

 by the naked eye ; but it may, nevertheless, be 

 examined with advantage by a low microscopic 

 power. The seed is covered on the outside with 

 a membrane, which is called the " testa." This 

 membrane is often curiously marked, and the whole 

 seed may be examined as an opaque object with 

 the low powers of the Microscope. In order to 

 do this, the light must be shut off from the mirror, 



