THE STAMENS. 



77 



this study. Having done this, you are only to find your 

 way back through the petaloid sepals, or sepal-like petals, 

 to the green leaf again. A series of these transitions 

 from the Pond-Lily, is shown at figs. 11 and 18. 



421. THE FILAMENT has a great variety of forms. 

 It is usually a slender, thread-like body, generally some- 

 what flattened, occasionally marked by other peculiarities, 

 and not unfrequently wanting. It is greatly thickened 

 in the Barberry and Melon, figs. 5 and 14; and is often 

 petaloid in the Pond-Lily, figs. 11 and 18. In regard to 

 color, it is usually white, but sometimes blue, yellow, or 

 red. The filament is not an essential organ ; and when 

 absent, the anther is said to be sessile. 



422. THE ANTHER has its normal position on the 

 summit of the filament. It generally consists of two 

 lobes or cells, which are united by a continuation of the 

 filament, called the CONNECTILE ; and the line of this 

 connection is marked by a groove, more or less strongly 

 defined, between the lobes. Each lobe is also marked 

 by a furrow, running through its sides or face from top to 

 bottom. This is called the Suture, or LINE op DEHIS- 

 CENCE ; and though the line itself is not well defined in fig. 

 1, its situation may be seen by the direction of the pollen. 



423. THE MODE OF ATTACHMENT of the anther to its 

 filament has given rise to three distinctions, which are of 

 considerable importance in analytical observations. The 

 anther is 



(1) INNATE, when the connectile rests firmly on the 

 summit of the filament, with no distinction of back or 

 front, as in fig. 1 ; 



(2) ADNATE, when the filament is connected with the 

 anther lobes by their whole length on one side, usually 

 called the back, as in the Iris, fig. 9 ; and 



(3) VERSATILE, when it is fixed to the filament by a 

 mere point, on which it lightly swings, as iii the Lily 

 and Grasses, figs. 17 and 6. 



424. The line of dehiscence is always lateral in the 

 innate anther, as in fig. 1 ; but in the adnate form, it is 

 opposed to the line of adhesion between the lobes and 

 their connectile, and hence it must occupy what is termed 

 the face. When the face of an adnate anther looks 

 toward the pistil, it is called INTRORSE (turned inward}. 

 When it looks away from the pistil, or toward the petals, 

 it is EXTRORSE (turned outward). The first of these 

 forme is seen in the Pond Lily, figs. 11 and 18; the 

 second in the Iris, fig. 9. 



Good subjects for illustration. Forms of the Filament when not present T 

 Normal position of the Anther of what generally consist f By what are the 

 obes nnlted-what called how marked ? How are the lobes marked ? In 

 the mode of Attachment how many varieties? Describe each, with examples, 

 tine of Dehiscence bow In the Innate anther In the Adnate when it looks 



425. The dehiscence of the anther presents many 

 irregularities. In the Barberry, fig. 5, which is a peculiar 

 form of the adnate variety, the anther opens by two 

 valves, that swing up as if by a hinge, like a trap-door. 

 In the Laurel family there are four such valves. The 

 anther of the Alchemilla opens transversely ; and in the 

 Potato and Heath tribes, the dehiscence is by pores at 

 the summit, as in a species of Nightshade, fig. 2. 



426. The Connectile exhibits several peculiarities. 

 It is sometimes developed into a kind of beak, as in 

 Asarum; in the Oleander, fig. 4, it is prolonged in a 

 plumose appendage ; it is forked in the Linden, so as 

 completely to separate the anther lobes ; in the Violet, 

 it is prolonged backward into a kind of spur; in the 

 Sage, it sits on the apex of the filament, like an inverted 

 bow, with its extremities pointing upward, and tipped 

 by the widely separated anthers ; and in many cases it 

 is almost or wholly wanting, so that the anther lobes are 

 united on the summit of the filament. The connectile 

 may be considered the mid-vein of the transformed leaf. 

 In the Melon, fig. 14, the anther lobes are waved or 

 sinuous. Versatile anthers are also termed iutrorse, 

 when their line of dehiscence looks toward the pistil, as 

 is the most common case, and extrorse in the reverse 

 position. 



427. The Pollen grains are usually spherical or ellip- 

 tical, but sometimes they are square, triangular, flattened, 

 cylindrical, or shaped like an hour-glass. But the most 

 curious of all forms is that of the Zostera, a sea-plant, 

 common along our coasts, in which they seem to be spun 

 out into long, smooth, shining threads, not unlike a skein 

 of bright glossy silk. 



428. Each pollen grain has two coverings, the outer- 

 most of which is called the EXTINE, and the innermost 

 the INTINE. 



429. THE EXTINE is a firm membrane, generally 

 smooth, but frequently covered with bristles and rough 

 points, as in fig. 10, and sometimes with banded reticu- 

 lations. 



430. THE INTINE is thin, delicate, and incapable of 

 extension. If a grain of pollen be immersed in water 

 the extine bursts, while the intine is protruded at one or 

 more points, for a purpose which will be explained in 

 treating of the functions of this and its kindred organ. 



43 1. In. the interior cavity of every pollen grain there 

 is a collection of very minute granules, which are found 



toward the Pistil f Away from the Pistil f Define Extrorse Introrsc. Irregu- 

 larities of Dehiscence how In the Barberry Alchemilla Potato and Heath 

 tribes? How Is the Connectile In the Asarum the Oleander the Sage? 

 Common forms of Pollen grains. Other forms. Zostora. Coats of tbe Pollen 

 the outer the Inner. Describe each. What ID the Interior cavity ? 



