EEPRODUCTIVE TISSUES. 



147 



day time and cold at night. (Haber- 



landt, p. 325.) 

 Haberlandt classes the organs of this 



system as follows: 



(a) Secretory organs, glands, external 

 and internal channelled organs for resin, 

 oil, mucilage and gum. 



(b) Excretory organs, nuicilage, resin 

 and oil holders, tannin and crystal sacs. 

 Intercellular excretory reservoirs. 



Glands. These may be external or in- 

 ternal. The external glands are gen- 

 erally at the extremity of epidermal 

 hairs, which at times are quite short. 

 They may be one celled or composed of 

 many cells. Mint. (Fig. 51.) By the 

 gradual filling up of the secretory cells 

 these glands grow larger, forming dis- 

 tinct sacs, filled with the secretion. The 

 ethereal oils are generally found in such 

 reservoirs. 



OfTicial plants bearing external glands 

 are Hyoscyamus, Tabacum, Mentha, 

 Thymus, Lavandula, Humulus, Matri- 

 caria, Achillea, Arnica, Absinthium. Ka- 

 mala. etc 



Internal Glands and Excretory Cells 

 are the names given to a number of 

 cells varying in shape and size which 

 are generally contained within the par- 

 enchymatic tissues of the plant organs. 

 They are generally large sac-shaped cav- 

 ities filled with secretions, oils, mucilage, 

 etc., and are generally designated ac- 

 cording to the character of their con- 

 tents. The most prominent are those of them. 



CHAPTER IX. 



containing resin, oil and crystals. Such 

 secretory organs are to be found in 

 Rhizomes, Calamus, Zingiber, Galangal, 

 Curcuma, Zedoary, Cortex Cascarilla, 

 Angustura, Radix Valerian, Folia Lau- 

 rus, Sassafras, Matico, Fructus Cubeba, 

 Cardamomum, Sinapis, etc. (Fig. <^^') 



Channelled Secretory Organs. These 

 are generally formed in the intercelhilar 

 spaces of the plant. They are much elon- 

 gated and are surrounded by secretory 

 cells. Conifers, Umbellifereae. 



Secretory Vessels are formed in the tis- 

 sues of the plant by the coalescence of 

 a number of secretory cells, thus mak- 

 ing irregular tubes which may be 

 branched or unbranched. These general- 

 ly contain the so-called milky juices, and 

 are met with in the Enphorbiacejr, 

 Asclepiadacere, Campanulaoea3, Lo- 

 beliaceae, Papaveracejie and Apocynacese. 



^^^- ^-^ 11 .V ■ u 1 



Crystal Cells are generally thm-walled 

 and sometimes cutinizcd or subcrized. 

 They varv according to the shape of the 

 contained' crystals, being rather regular 

 in those containing rhapides. 



Tannin occupies the typical paren- 

 chymatic cells of the plant, which, when 

 so employed, are generally suberized and 

 have a brownish or reddish appearance. 



The study of tho>se portions of the 

 plant devoted to excretion and secretion 

 are as vet little understood, and the stu- 

 dent is referred to the bibliographical 

 references for a more complete account 



REPRODUCTIVE TISSUES. 



There are few types of tissue that 

 have not at least been touched upon in 

 the foregoing pages, and although there 

 are no essential differences in the tis- 

 sues of reproduction, it is, nevertheless, 

 of advantage to recapitulate somewhat 

 concerning them. The organs of repro- 

 duction are the pistils and the stamens, 

 and each have some elements that are 

 of use in a practical determination of 

 many drugs, such as the official herbs, 

 flowers, fruits and seeds. In herbs and 

 flowers the pollen grains are the only ele- 

 ments that have not received some at- 

 tention; they will therefore be treated 

 somewhat hastily in this place. 



Pollen Grains originate by cell division 

 in the anther sacs. When mature they 



vary greatly in shape, size, color and 

 markings. Specimens of drugs that are 

 to be examined for pollen grains shmild 

 be placed in some oily substance, as this 

 preserves the mnrkings of the grains bet- 

 ter than water. Specimens may also be 

 examined in water, as many of the older 

 figures of pollen grain were made from 

 -rains that had been examined m that 

 medium. The differences in the shapes 

 and other peculiarities of the grains of 

 the official herbs and flowers it is im- 

 possible to treat of in this place but the 

 student is called upon to bear their mi- 

 mrtance in mind, and is referred a treat- 

 Fse on "Pollen" by U, Pakenham Edge- 

 wortl, London, 1877, where the htera- 

 5re of the subject up to that time is 

 given. 



