lO 



HARDWICKE'S SCIENCE-GOSSIP. 



NOTES FOR SCIE^•CE CLASSES. 



THE chief instruction given in our popular 

 Science Classes is intended to be practical ; 

 a few hints to students will just now be welcome. 

 Blackboard illustration is no doubt useful in its place, 

 but if the student can see an actual specimen under 

 the microscope, and have each part of the section 

 carefully explained (all the better if the section can 



Fig. i:.— Transverse Section of Lime-twig. i. Epiderrnis, 

 formed of minute cells, without chlorophyll. 2. Cortical 

 ground-tibsuc, containing chlorophyll. 3. PhlOem, composed 

 of hard and soft-bast. 4- Cambium, veiy bright-looking 

 cells ; this often disappears in roughly-cut seciions. s- Xylem, 

 formed with spiral and dotted vessels, or the first year's ring 

 of wood. 6. Medullary sheath, immediately surrounding the 

 column of pith. 7. Pith, composed of ground or fundamental 

 tissue. S. Medullary ray, crossing the xylem, and ending 

 with a wide opening in the phloem. 



F'fi. '3 — Transverse Section of Rjisciis stem. i. Epiderm's. 

 2. Cortical layer of ground tissue. 3. Sclerenchyma ; observe 

 this part with care, and compare it with section of Pteris. 

 4. Ground or fundamental tissue. 5. Fibro-vascular bundle 

 .scattered amongst the ground tissue ; observe the xylem, 

 always towards the centre of the stem. Also, trace out 

 from .-» very highly-magnified fibro-vascular bundle the same 

 parts as in Lime. 



be made in the class-room in his presence), then work 

 it all out at home by reading a good text-book, the 

 subject then becomes intensely interesting ; such 

 students are not only content with making a good 

 position in the examination, but it becomes a life- 

 long .study. Our notes are intended merely to make 

 the suVjject plain and simple, so that it may have 

 general interest, and to fdl up a felt want in most 

 text-books in use at the present time ; therefore we 

 have marked each distinct part in the following sec- 



tions, and give the names of the different portions a? 

 understood in our present advanced state of the 

 science, and as specially indicated in the syllabus. 

 To know each part, and tell where to find it, is the 

 key to its structure, and if our readers will practically 

 work out the three stems described, they have made a 

 firm step towards success. 



The specimens selected are the best for the pur- 

 pose, and can be found in eveiy district. 



Fig. 14.— Vascular bundle of Rnsciis. i. 

 2. Xylem. 3. Cambiform tissue, or soft-bast 

 or bast-fibres. 



Ground tissue. 

 , 4. Hard-bast, 



Fig. 15. — Transverse Section of Rhizome of Pteris. i. Scleren- 

 chyma ; this is a brown cellular tissue in three distinct 

 layers. 2. Fibro-vascular bundles ; here note position and 

 structure as pointed out in the next engraving ; but in the 

 entire section, by means of a low power, they should be first 

 studied. 3. Ground tissue. 4. Epidermis. 



The first is a section of the lime-tree, and is a 

 guide to the structure of all Dicotyledonous stems. 

 First, trace out in an actual specimen the position 

 of the fibro-vascular ring, in the following order, viz., 

 Phloem, Cambium, and Xylem, commencing fronv 

 the epidermis, then trace them out in the same po- 

 sition in the butcher's-broom (Rusais aaileati/s, L.) 

 stem, and so on with the common brake-fern (Pteris). 

 Second, examine carefully the Phloem of the lime. 



