NITROGENOUS CELL CONTENTS. 



117 



starch grain, which is the great reserve 

 for carbohydrate material of the plant, 

 Aleurone grains vary considerably iu 

 size and shape, from round to elliptical, 

 egg-shaped, or some times crystal-like in 

 form, (a) In general they nro colorless, 

 sometimes brownish, greenish or yellow- 

 ish. They are found abundantly in seeda 

 and especially in oily nuts, often making 

 up from 10 to 25 per cent, of such nuts 

 as the almond and Brazil nut. 



FiK. 10.— Aleurone jrrains from the seeds of 1 

 and 2~-Bertholletia excelsea. 3, Ricinus com- 

 munis, acted upon by water. 4, Elaeis jjum- 

 densis. 5, Myristica f raj;rans. 6. Cannabis sa- 

 liva. 7, Datura Stramonium. 8, Gossypium 

 spec. 9 and 1(», Cydonia vulgaris. 11, 12 and W, 

 Amyf?dalus commnnis. 14, Phaseolua vulgaris. 

 15. Coriandrum sativum. 16. Vitis Venifera, 17, 

 Foeniculum (Tschlrch) reduced, 



(a) Morphologically the Aleurone 

 grain consists of 1. the Membrane, 2. 

 The Mass of the Grain. 3. The Inclu- 

 sions. These may be crystalloids, glo- 

 boids, or oxalate of calcium crystals. 



(c) THE PLASTIDS. These bodies in 

 great part are the active builders of plant 

 tissues. They are universally distributed 

 throughout the vegetable kingdom, fail- 

 ing to any great extent only in the fungi. 

 We distinguish two types: 



1. liGUCoplastids. White or colorless. 



2. Chromoplastids. Variously colored. 

 Green, blue, yellow, red, etc. 



1. The Leucoplasts are small, color- 

 less albumenoid bodies widely distn'but- 



(a) For motbnds of staining the alt;^;f^iJ5 

 grains, see Zimmermauu, Botanical Micro- 

 technique, 



ed in plants. They are the first steps in 

 the building up of the Chlorophyll grain 



and through this to the starch grain. 

 They are quite minute in size, and are 

 most abundant in roots, especially in 



those roots that not only are storehouses 

 for starch, but which also manufacture 

 some, as Iris. 



2. The Chromoplasts include a num- 

 ber of diverse elements, the most im- 

 portant one of which is the Chlorophyll 

 grain. The Chlorophyll grains are the 

 main organs of assimilation of the plant; 

 by them the active energy of the sun's 



Fiff. 11.— Leucoplastids in Rhizome of Iris, in 

 process of forming starch. (Tschlrch.) 



rays is converted into potential energy 

 and is stored up in the starch grain 

 which the Chlorophyll grain is making 

 at the same time from the carbon di- 

 oxide of the air and the water that 

 comes from the root. 



In many of the lower forms of plant 

 life the chlorophyll grain is irregular in 

 shape, but in the higher forms from the 

 mosses upward they are rounded or 

 slightly oval. In size they vary from 3 



to 11 micro, m. 



The structure consists of a protein 

 body substance similar in all respects 



Fie 12. -Cells of an alga showing spiral band- 

 shaped chlorophyll grains. 



to a leucoplast. This is somewhat 

 spongy and is infiltrated with the color- 

 in- matter, which is generally green; the 

 whole is often enclosed in a dehcate al- 

 bumenous membrane. ^ ^ 



While the chlorophyll gram is usually 

 found only in the vegetable kingdom, it 

 is not exclusively its own, for there are 

 a number of the lower animals, Pro- 



